Climate Change Mitigation as an Obligation Under Human Rights Treaties?

Abstract

Judges and scholars have interpreted human rights treaties as obligating states to mitigate climate change by limiting their greenhouse gas emissions, an argument instrumental to the development of climate litigation. This Article questions the validity of this interpretation. A state's treaty obligation to protect human rights implies an obligation to cooperate on the mitigation of climate change, the Article argues, only if and inasmuch as climate change mitigation effectively protects the enjoyment of treaty rights by individuals within the state's territory or under its jurisdiction. As such, human rights treaties open only a narrow window on the applicability of general mitigation obligations arising under climate treaties and customary international law.

I. Introduction

States have recognized that climate change and its adverse effects, a common concern of humankind, call for international cooperation.¹ Mitigating climate change requires substantial efforts to limit and reduce greenhouse gas (GHG) emissions at a global scale.² But while it is collectively rational for states to invest in substantial efforts to mitigate climate change, it is individually rational for each state not to cut its own emissions, instead seeking to free ride on the mitigation outcomes achieved by others.³ This collective action problem is compounded by the absence of objective formulae to determine the requisite level of global mitigation action and to allocate the efforts necessary to achieve it.⁴ States have long acknowledged that, as a whole, they are failing to spur sufficient mitigation action, but they are yet to increase their individual commitments accordingly.⁵ Domestic litigation is increasingly viewed as a way to overcome the failure of international negotiations.⁶

States have broad obligations to mitigate climate change under international environmental treaties,⁷ and possibly even broader obligations under customary international law,⁸ but plaintiffs typically lack standing to invoke any of these obligations.⁹ Rather, when climate litigation is based on international law,¹⁰ it generally relies on human rights treaties.¹¹ As human rights treaties require states to take measures to protect human rights, and as climate change hinders the enjoyment of various human rights, there is at least a plausible argument that human rights treaties may imply an obligation for states to mitigate climate change.

This argument has received considerable support in recent years, particularly from UN human rights treaty bodies. The Committee on Economic, Social and Cultural Rights (CESCR) has suggested that, “[i]n order to act consistently with their human rights obligations,” states parties should revise the nationally determined contributions (NDCs) to global mitigation action that they have communicated under the Paris Agreement.¹² The Committee on the Elimination of Discrimination against Women has asserted the existence of an obligation for states “to effectively mitigate . . . climate change in order to reduce the increased disaster risk.”¹³ These two treaty bodies were joined by three others in issuing a statement according to which, to comply with human rights treaties, states “must adopt and implement policies aimed at reducing emissions . . . which reflect the highest possible ambition.”¹⁴ Consistently, treaty bodies have included recommendations for policies and measures on climate change mitigation in their concluding observations on national periodic reports.¹⁵

Developments have also been taking place at the national level, generally in relation to civil and political rights. In Urgenda, the Supreme Court of the Netherlands has held that the state's obligation to protect the right to life and the right to private and family life under the European Convention on Human Rights (ECHR) implied an obligation to reduce its GHG emissions by at least 25 percent by the end of 2020 compared with 1990 levels.¹⁶ By contrast, in Natur og Ungdom, the Supreme Court of Norway found that the issuance of ten petroleum production licenses did not involve a “real and immediate” threat on the rights to life or to private and family life under the ECHR,¹⁷ although the Court may not necessarily have arrived at the same conclusion if the challenge had been directed more broadly at national mitigation policies.¹⁸ Claims based on mitigation obligations implied from human rights treaties are currently pending before other national courts,¹⁹ the European Court of Human Rights,²⁰ and two treaty bodies.²¹ Comparable cases have also been made on the basis of constitutional rights,²² leading often to similar analyses.²³ While some cases have been dismissed on procedural grounds—for instance with regard to particular conceptions of the separation of powers²⁴ or for lack of standing²⁵—others will likely be decided on the merits in the years to come.

The relevant literature is largely supportive of the interpretation of human rights treaties as the source of mitigation obligations.²⁶ Michael Burger and Jessica Wentz, for instance, note the existence of a “growing consensus that a mitigation obligation does exist under international human rights law.”²⁷ Doubts, however, have occasionally been raised. More than a decade ago, a report by the UN high commissioner for human rights conceded that, “[w]hile climate change has obvious implications for the enjoyment of human rights, it is less obvious whether, and to what extent, such effects can be qualified as human rights violations in a strict legal sense.”²⁸ Lavanya Rajamani observed that many negotiators “were skeptical of the utility of a human rights approach, given the complex and laden agenda of the climate process, and the limited space for new methodological or conceptual approaches.”²⁹ Alan Boyle suggested that the causes, effects, and responsibilities associated with climate change “are too numerous and too widely spread to respond usefully to individual human rights claims or to analysis by reference to particular human rights.”³⁰ Fanny Thornton asked whether the causal links between a state's mitigation action and the enjoyment of human rights may be “too intricate and diffuse” to ground a convincing legal case.³¹ These views recognize that climate change differs in many respects from the issues to which human rights law has generally been applied: responsibilities are diffuse, there is no distinct class of victims, and overall a state's action on climate change mitigation, by itself, is never a quick or effective fix.

This Article builds on these prior doubts to assess the possibility of interpreting human rights treaties as the source of a state's obligation to mitigate climate change. The analysis presented here is critical but constructive. The Article suggests a new, plausible way—consistent with the tenets of treaty interpretation—to construe human rights treaties as the source of an obligation to mitigate climate change, albeit only in very limited circumstances. The Article submits that, to comply with its treaty obligation to protect a human right, a state must cooperate on the mitigation of climate change only if and only inasmuch as climate change cooperation may effectively protect the enjoyment of the right at issue by individuals within its territory or under its jurisdiction. While international human rights law may thus have a role to play in the mitigation of climate change under certain circumstances, this role is far more limited than what judges and scholars have suggested so far.

Part II outlines the relevant conceptual background on the relation between climate change mitigation and human rights treaties. By contrast with the general obligations on climate change mitigation that arise from international environmental agreements or customary law, human rights treaties provide a bizarre, frequently ill-fitting legal ground to envision states’ obligations to mitigate climate change—one that tends to emphasize the direct, local, short-term costs of mitigation action within the state's territory rather than its more diffuse, global, long-term benefits. One can debate whether human rights treaties were ever intended to regulate such diffuse impacts. Nevertheless, and despite the absence of identifiable victims of climate change, human rights treaties may enable the use of some implementation mechanisms not otherwise available in relation to general mitigation obligations.

Part III demonstrates the possibility of identifying mitigation obligations on the basis of human rights treaties. The key problem it addresses is that human rights treaties require states to protect human rights mainly within their own territory, thus remaining insensitive to most of mitigation action's global benefits. Contrary to prevailing theories, this problem cannot be overcome by extending the extraterritorial application of human rights treaties, by interpreting international law as imposing “collective obligations,” or by reference to states’ general international law obligation to cooperate on matters of international concern (an other-regarding obligation of cooperation). The problem, however, can partly be addressed by understanding that a state's obligation to protect human rights implies an inward-looking obligation of cooperation: a state must cooperate on climate change mitigation in good faith if—assuming other states follow the same precept—this can be anticipated to help protect the rights of individuals within its territory and under its jurisdiction.

Finally, Part IV discusses how the mitigation obligations derived from human rights treaties are to be interpreted. Under the principle of systemic integration, the interpretation of implied mitigation obligations should take into account other relevant norms, including general mitigation obligations arising under climate treaties and customary international law. Scholarship and judicial practice have misconstrued this principle when assuming that, for a state to comply with its mitigation obligation implied from a human rights treaty, it must fully comply with all its general mitigation obligations. Rather, the Article suggests that human rights treaties open only a certain window onto the applicability of general mitigation obligations. The size of this window of applicability varies according to the treaty, the right, and the national circumstances at issue—in particular, the potential benefits of mitigation action for the enjoyment of the right within the state's territory and under its jurisdiction. As no human rights treaty fully comprehends the benefits of climate change mitigation for human welfare, future generations, and ecological resources, implied mitigation obligations can only open a narrow window on the applicability of general mitigation obligations.

II. The Relevance of Human Rights

This Part includes introductory observations about the relevance of human rights to climate change mitigation. First, it explores the ambivalent relation between climate change and the enjoyment of human rights: while climate change hinders the enjoyment of human rights, this is also true of action taken to mitigate climate change, the “cost” of which for the enjoyment of human rights tends to be more local and immediate than its “benefit.” Second, this Part discusses the strategic procedural advantages of human rights law from the viewpoint of potential plaintiffs, noting that the difficulty of attributing any “victims” to a state's failure to mitigate climate change may hinder access to some (but not all) of the judicial and quasi-judicial procedures generally available under human rights treaties.

A. The Ambivalent Relation Between Climate Change Mitigation and Human Rights

1. The Human Rights Impact of Climate Change

Human rights treaties create two types of obligations: negative obligations to “respect” (i.e., to refrain from violating) human rights and positive obligations to “protect” and “fulfill” human rights.³² Some human rights treaties specifically point to the obligation of states “to take the necessary steps . . . to adopt such legislative or other measures as may be necessary to give effect to” human rights,³³ or simply to “take all appropriate measures to ensure” that individuals can enjoy their rights.³⁴ More generally, a state must take appropriate measures to address any threat to the enjoyment of human rights, whether this threat is of human origin (e.g., crime) or triggered by a natural event (e.g., a natural disaster).³⁵ Positive human rights obligations are obligations of conduct: a state can be held responsible for a wrongful act only if it fails to exercise due diligence, notwithstanding the consequences.³⁶

The fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC) reflects the global scientific consensus that climate change has “caused impacts on natural and human systems”³⁷ by increasing the frequency or severity of some extreme weather events, reducing the availability of freshwater resources, and affecting ecosystems, food production, human health, livelihood, and poverty, among other things.³⁸ Many of the effects of climate change hinder the enjoyment of human rights, including civil and political rights (e.g., rights to life and to property),³⁹ economic, social, and cultural rights (e.g., rights to an adequate standard of living and to the highest attainable standard of health),⁴⁰ and third generation rights (e.g., when applicable, the right to a healthy environment).⁴¹ Climate change could well be, as Mary Robinson famously suggested, “the greatest threat to human rights in the twenty-first century.”⁴²

States’ obligation to protect human rights must be informed by scientific knowledge about the current and predictable impacts of climate change. The first and most obvious implication is that states must implement measures to promote adaptation to climate change.⁴³ Some of the impacts of climate change can be avoided or reduced, for instance, by preventing urban development in coastal regions that will be affected by sea-level rise or through early-warning systems aimed at reducing the vulnerability of populations to extreme weather events.⁴⁴ A state can generally implement such measures on its own, although some states may need international financial or technical assistance. As many of the impacts of climate change affect the enjoyment of human rights, states’ obligation to protect human rights can be interpreted as an obligation to take adaptation measures to avoid or reduce these impacts. Accordingly, the High Court of Lahore pointed out that a state's “delay and lethargy” in implementing adaptation action could constitute a breach of its human rights obligations.⁴⁵ However, adaptation is insufficient to prevent the increasingly harmful consequences of ongoing GHG emissions. As the IPCC noted, the existence of “biophysical limits to adaptation” and constraints of costs and resources mean that “adaptation cannot generally overcome all climate change effects.”⁴⁶ Adaptation action needs to be complemented by mitigation action.

A second implication of our knowledge of climate change could be that, in order to protect the enjoyment of human rights, states should promote the mitigation of climate change by taking measures to reduce GHG emissions.⁴⁷ The Human Rights Council's special procedure mandate-holders have suggested that human rights treaties require states “to adopt the mitigation measures necessary to reduce global emissions so as to hold the increase in global temperature below levels that would cause widespread harm to the enjoyment of human rights.”⁴⁸ A similar reasoning led the Supreme Court of the Netherlands, in Urgenda, to interpret the obligation of states to protect the right to life and to private and family life under the ECHR as implying an obligation to mitigate climate change.⁴⁹

However, the benefits of a state's mitigation action for the enjoyment of human rights are not as direct, immediate, and predictable as those of adaptation action. With adaptation action, a state may achieve some effective human rights benefits for its population, for instance by establishing early-warning systems that help reduce casualties in the event of a natural disaster⁵⁰ or by implementing various policies to support food production when it is threatened as a consequence of climate change.⁵¹ By contrast, a national mitigation policy aimed at reducing the state's GHG emissions can only have a minor influence on the global rate of GHG emissions (“flow”), and this will only gradually reflect on the atmospheric concentrations in GHGs (“stock”) that cause climate change, so that such policy will achieve very little, if any, tangible human rights benefits for the state's population.⁵² Thus, while a state may adapt to climate change by implementing national policies on its own, effective mitigation action requires international cooperation in order to achieve significant cuts in GHG emissions at the global scale. And while adaptation action may achieve tangible outcomes in the short- to medium-term, the full benefits of mitigation action can only unfold in the long term, when years-long emission reductions efforts start reflecting in lower-than-expected GHG concentrations in the atmosphere.

2. The Human Rights Impact of Mitigation Action

Climate change mitigation could possibly have three types of impacts on the enjoyment of human rights. Firstly, the implementation of mitigation action can involve human rights violations, for instance the forcible relocation of populations to give room to a hydroelectric project⁵³ or to the production of biofuel.⁵⁴ However, states have an obligation to comply with their human rights obligations when implementing mitigation action, and there is no inevitable conflict between the protection of human rights and the mitigation of climate change.⁵⁵ Human rights violations in the process of implementing mitigation action can, and must, be prevented.

Secondly, climate change mitigation may sometimes be presented as one of the objectives of general interest which human rights treaties recognize as justifying limitations to the protection of rights—along with national security, public order, and economic development. For instance, climate change mitigation could arguably be taken to justify (under conditions of necessity, proportionality, and legality) hydroelectric projects involving land expropriation or even population displacements, which would otherwise be incompatible with the state's human rights obligation.⁵⁶ Besides, the recognition of a “climate emergency” by various national institutions in recent years⁵⁷ suggests the need for exceptional measures that could conceivably include derogations from human rights.⁵⁸ In fact, climate change mitigation is perhaps more naturally framed as an objective justifying limitations of and possibly derogations from human rights, rather than as a way to protect the enjoyment of individual rights—but one does not necessarily exclude the other.⁵⁹

Thirdly, and overall, climate change mitigation involves a massive redeployment of resources, which will inevitably compete with other priorities relevant to the protection of human rights, even when this does not translate directly into any human rights limitations.⁶⁰ At times, mitigation action may compete with other policies for the use of natural resources: for instance, mitigation strategies relying heavily on biofuel or on negative emission technologies would increase demand for land and water, with potential impacts for the rights to food and water.⁶¹ Other mitigation strategies may increase the price of energy,⁶² with potential adverse effects on poverty.⁶³ In more general terms, mitigation action is expensive⁶⁴ and it will require financial investments at a pace and scale that imply substantial costs of opportunities for the pursuance of other policies.⁶⁵ Developed states, for instance, have pledged to mobilize jointly U.S.$100 billion per year by 2020 to support climate action,⁶⁶ and they have decided to set a higher goal post-2020.⁶⁷ The IPCC estimated that, under the most cost-effective scenarios, mitigation action could entail global consumption loss of 1.7 percent by 2030 and 4.8 percent by 2100.⁶⁸

The ability of a state to effectively protect human rights is resource-dependent,⁶⁹ and some of the resources that states invest in reducing GHG emissions are inevitably taken away from other priorities, including priorities that advance the protection of human rights. As an immediate budgetary constraint, mitigation action perhaps more obviously hinders efforts to protect social and economic rights, such as the rights to an adequate standard of living, to the highest attainable standard of health, or to education;⁷⁰ but it also affects the effective protection of civil and political rights as states may not, for instance, be able to invest as much in road safety, crime prevention, or the justice system, when they are massively investing in mitigation action.⁷¹

There is indisputable evidence that, from a global utilitarian perspective, the costs of mitigation action are justified by its benefits: humankind is certainly better off investing in stringent measures to reduce GHG emissions than enduring the increasingly severe impacts of climate change on individuals, societies, and ecosystems for centuries to come.⁷² States have acknowledged that it is in their common interest to implement “an effective and progressive response to the urgent threat of climate change.”⁷³ Justifications for climate change mitigation, however, are expressed in terms of global utility, for instance by reference to economic development, food production, or human security.⁷⁴ By contrast, human rights treaties require each state to protect the rights of individuals within its territory and under its jurisdiction, not to maximize global utility. The lenses that human rights treaties offer tend to magnify the immediate, proximate costs of a state's mitigation action—that are borne primarily by the individuals within the state's territory—while being unable to fully appreciate the utility of such action—the global, diffuse, long-term benefits for individuals, societies, and ecosystems that justify mitigation action from a broader policy perspective. In other words, human rights treaties miss a large part of the picture when it comes to justifying mitigation action.⁷⁵

B. The Strategic Advantages of Human Rights Law

Human rights treaties provide neither the only nor the most compelling legal basis to claim that states ought to mitigate climate change. Virtually every state is party to the UN Framework Convention on Climate Change (UNFCCC) and to the Paris Agreement. Under the latter, states have committed to communicate successive NDCs and to take appropriate measures to achieve their objectives.⁷⁶ While it is largely understood that the NDCs that have been communicated to date lack ambition,⁷⁷ it remains that every party to the Paris Agreement has also a general (albeit ill-defined) obligation under the UNFCCC to formulate and implement measures on the mitigation of climate change.⁷⁸ This general mitigation obligation is arguably to be read in the context of the growing expectation, expressly reflected in the Paris Agreement, that each state will communicate NDCs that “reflect its highest possible ambition.”⁷⁹ Climate treaties thus provide at least a plausible legal basis to challenge a state's lack of ambition on climate change mitigation.

In addition, states have a customary international law obligation to exercise due diligence to protect the rights of other states,⁸⁰ including by taking appropriate measures to prevent significant transboundary environmental harm.⁸¹ If interpreted from an inductive or “traditional” approach, in light of the general practice of states, this obligation would presumably not require any particular state to implement mitigation actions with levels of ambition exceeding those followed by most other states. A deductive or “modern” approach could however suggest a more demanding obligation,⁸² in light, perhaps, of the objective of holding global warming within 2 or even 1.5 °C above pre-industrial temperatures—an objective states agreed upon in the Paris Agreement⁸³—if this objective can be construed as a necessary implication of states’ general mitigation of due diligence.⁸⁴ The Draft Conclusions on the identification of customary international law adopted by the International Law Commission in 2018 emphasize the inductive approach without denying the complementary role that the deductive approach has played in judicial practice.⁸⁵

The interest for human rights treaties in relation to climate change mitigation stems in no small part from the access they provide to litigation and other complaint mechanisms.⁸⁶ Neither the UNFCCC nor the Paris Agreement has an effective mechanism to review compliance,⁸⁷ while the prospects for international litigation on general mitigation obligations are limited by the voluntary nature of international dispute settlement and (to a lesser extent) by the limited incentive for a state to initiate contentious proceedings against another with respect to an erga omnes obligation.⁸⁸ By contrast, human rights treaties provide potential plaintiffs with various institutional and procedural advantages. In addition to establishing state-to-state dispute settlement and complaint mechanisms,⁸⁹ human rights treaties often allow individuals, and sometimes groups, to file complaints before international bodies or cases before regional human rights courts,⁹⁰ while treaty bodies periodically review and make concluding observations on national reports.⁹¹ Overall, human rights treaties or their instrument of incorporation allow individuals or groups to claim standing regarding the performance of a state's obligation before domestic courts, whereas they would typically have no standing to directly invoke climate treaties or customary law.⁹²

A major procedural caveat, however, is that applicants claiming the implementation of a state's obligation under a human rights treaty are often required to prove that they are, or would imminently become, the “victims” of a human rights violation.⁹³ This condition has already been a hurdle in simpler cases concerning local environmental harm,⁹⁴ where admissibility was limited to applicants who were “directly and seriously affected”⁹⁵ or otherwise could prove “a reasonably foreseeable threat to” their rights.⁹⁶ The relevant cases admitted by the European Court of Human Rights, for instance, typically concern individuals affected by a disaster⁹⁷ or directly exposed to a major local source of pollution,⁹⁸ rather than those exposed to more diffuse environmental harms. The condition of victimhood is particularly problematic in climate litigation. Climate change hinders the enjoyment of human rights in a diffuse fashion; it may rarely, if ever, be possible to consider someone a “victim” (whether actual or potential) of climate change—and, a fortiori, of a state's failure to implement the requisite mitigation action.⁹⁹

Arguments aimed at overcoming this challenge have sometimes relied on scientific studies regarding probabilistic event attribution to suggest the possibility of identifying “victims” of climate change.¹⁰⁰ However, scientists are divided about the soundness of such studies and, even more, about their relevance to litigation.¹⁰¹ At any rate, attributing a weather event to climate change is only one of the links in the causal chain that must be established to prove that individuals are victims of a state's failure to take appropriate measures to protect their human rights. A weather event only affects an individual when, as the result of successive individual and collective decisions, this individual is exposed and vulnerable to the event. Thus, migration studies deny the possibility of identifying a discrete population of “climate migrants” on the ground that the influence of climate change on migration, albeit real, is diffuse and indirect.¹⁰² At the other extremity of the causal chain, attributing any “climate victim” to a state's conduct would require evidence that events affecting the individual were caused by the failure of that state to mitigate climate change, rather than by historical GHG emissions that took place before the scientific discovery of climate change, emissions of other states, or emissions that even the state's most stringent mitigation action would not have been able to prevent.

The absence of identifiable “victims” could strike a fatal blow to individual or group applications before regional human rights courts and complaints to treaty bodies. On the other hand, this caveat does not necessarily affect the other strategic advantages of human rights treaties, in particular the periodic adoption of concluding observations by treaty bodies or even the possibility of interstate complaint and dispute settlement procedures based on human rights treaties. Overall, domestic legal systems define their own conditions for standing, which are sometimes more favorable to the implementation of human rights treaties in the absence of identifiable victims, for instance when they permit public interest litigation. Thus, the Supreme Court of the Netherlands allowed Urgenda to invoke the ECHR in defense of a public interest even while noting that the association would lack standing before the European Court of Human Rights as “it is not itself a potential victim.”¹⁰³ Similarly, standing remained unchallenged in Natur og Ungdom,¹⁰⁴ as Norwegian law expressly allows public interest litigation by interested NGOs.¹⁰⁵ By contrast, the European Union's General Court dismissed as inadmissible a case challenging the compatibility of the European Union's 2030 mitigation target in light of the Charter of Fundamental Rights, in line with the limited conditions for standing under EU law,¹⁰⁶ on the ground that the applicants had not established that the legislation they sought to challenge could infringe their fundamental rights.¹⁰⁷ The Administrative Court of Berlin also denied standing, on comparable grounds, to individual farmers and an NGO that claimed that additional mitigation action was essential to protect fundamental rights.¹⁰⁸ The Supreme Court of Ireland denied standing to an NGO making similar claims on constitutional and conventional bases.¹⁰⁹ Meanwhile, the French State Council allowed standing to townships and associations representing public interests to challenge the legality of the state's mitigation action, but not to individuals pursuing their own interests.¹¹⁰

This procedural difficulty reveals a more fundamental questions about the limitations of human rights law and adjudication with regard to climate change mitigation. When no victim can be identified, human rights no longer act as a “trump” over objectives of general interest;¹¹¹ rather, what is framed as “human rights protection”—the mitigation of climate change—itself becomes, in fact, an objective of general interest, which competes with other such objectives and with the protection of individual rights. One may question whether human rights law permits a judicial cost-benefit analysis of these various objectives of general interest,¹¹² and more specifically whether human rights law can be interpreted as requiring states to pursue one such objective (with indirect human rights benefits) even if it comes at the expense of direct impacts on human rights. If so, how to ensure that the judicial process of interpreting and applying human rights law does not take over the political process of defining and balancing objectives of general interest? This question goes far beyond the scope of this Article, but it necessarily informs what, ultimately, one considers as the potential for human rights treaties to be interpreted at all as the source of an obligation to mitigate climate change.

III. The Identification of Implied Mitigation Obligations

This Part assesses whether human rights treaties imply an obligation to mitigate climate change. First, it identifies the difficulty of approaching the need for international cooperation in terms of human rights obligations: a state, acting on its own, is unable to achieve sufficient mitigation outcomes to effectively protect the human rights of individuals within its territory or under its jurisdiction. Second, it refutes three common arguments for the identification of implied mitigation obligations which rely, respectively, on (1) the extraterritorial application of human rights treaties, (2) the interpretation of human rights obligations as “collective obligations,” and (3) the existence of other-regarding obligations of cooperation as part of human rights treaties. Third, as an alternative theory, this Part submits that a state's obligation to protect a human right should be interpreted as implying a narrower, inward-looking obligation of cooperation, according to which a state must cooperate on the mitigation of climate change only to the extent that this may effectively benefit the enjoyment of that right by individuals within the state's territory or under its jurisdiction.

A. The Problem

Acting on its own, a state is not generally capable of achieving mitigation outcomes that will make any real difference for the protection of the human rights of individuals within its territory or under its jurisdiction.¹¹³ For instance, in Urgenda, the Netherlands was ordered to enhance its mitigation action in such a way as to achieve 9 percent reduction in its projected level of emission for 2020,¹¹⁴ that is, about 0.03 percent reduction in global GHG emissions that year.¹¹⁵ Even if the same increase of ambition had been imposed on China, the largest GHG emitter, it would have translated into only about 2 percent reduction in global emissions.¹¹⁶ Such incremental changes in global GHG emissions (a flow) would translate, after many years, only in very small differences in GHG concentration in the atmosphere (a stock), hence in very little tangible mitigation outcomes.

Incremental mitigation outcomes may unquestionably be worth achieving if one considers their diffuse, global, long-term benefits—even a tiny contribution to addressing “the greatest threat to human rights in the twenty-first century”¹¹⁷ should be welcomed, as addressing a tiny part of an enormous problem. Yet, most of these benefits do not fall within the scope of what human rights treaties require states to do. In particular, a key obstacle to interpreting human rights treaties as the source of an obligation to mitigate climate change is that a state's human rights obligations are generally limited to its jurisdiction or territory,¹¹⁸ whereas the impacts of climate change are global in nature.¹¹⁹ When one only takes into account the benefits of a state's mitigation action that take place within the state's own territory, these mitigation outcomes appear not just tiny, but vanishingly small.

It is therefore likely that, within a state's territory or under its jurisdiction, the costs of any ambitious mitigation action will outweigh its benefits. For instance, all other things being equal, the inhabitants of the Netherlands would surely be better off if additional mitigation action had not been imposed on the state, hence eventually on them: Urgenda imposed significant public expenditure, and presumably higher energy prices, on the state's residents,¹²⁰ for vanishingly small benefits for their human rights. A state (especially a small one), taken in isolation, would often do a better job at protecting the rights of individuals within its territory or under its jurisdiction by deciding not to burden them with mitigation action, investing instead in adaptation action or in various other policies that could achieve more tangible human rights benefits within the state's jurisdiction (e.g., police training, public education, or road safety). Thus embedded in human rights treaties is precisely the issue that has constantly plagued the UNFCCC negotiations: each state seeks to protect its own population—and, human rights treaties seem to suggest, is bound to do so—rather than pursuing their common interest in mitigating climate change.¹²¹

This problem is exacerbated by other limitations of human rights treaties: as these treaties focus on the rights of humans, they do not fully comprehend the utility of climate change mitigation for human welfare,¹²² future generations,¹²³ or ecological resources.¹²⁴ Yet, addressing these exacerbating factors would not solve the key problem of territorial limitation. Human rights treaties may well evolve toward the recognition of new rights (e.g., to a healthy environment)¹²⁵ but, as long as they remain treaties on the protection of human rights, they will maintain generally an individualistic approach to human welfare,¹²⁶ an anthropocentric approach to ecological resources,¹²⁷ and, overall, a territorial approach to state obligations,¹²⁸ thus remaining indifferent to important benefits of mitigation action beyond the treaty rights. Likewise, even if human rights treaties were to be interpreted as granting rights to “future generations,”¹²⁹ the cost that a state incurs when implementing mitigation action would often exceed the long-term benefits for present and future generations within its territory—most of the benefits that justify ambitious mitigation action in any one country are those that would be enjoyed by the future population living in other countries.

B. Invalid Solutions

Three main arguments have been made in attempts to overcome the problem described above and to justify the interpretation of human rights treaties as the source of an obligation to cooperate on the mitigation of climate change. The first argument is that human rights treaties create extraterritorial obligations relevant to climate change mitigation. The second argument is that states have “collective obligations” to protect human rights that require them to act in concert on climate change mitigation. The third argument is that human rights treaties include an extensive obligation for states to cooperate on the international protection of human rights, hence also on the mitigation of climate change. The following refutes these three arguments.

1. Extraterritorial Obligations

Scholars have highlighted the evolution of the case law regarding the extraterritorial application of human rights treaties to suggest that it could extend to the impacts of a state's failure to mitigate climate change.¹³⁰ But while the question of extraterritorial application has long been unsettled, it is now relatively well established that states’ human rights obligations apply extraterritorially only in limited circumstances—mainly where the state exercises “effective control” over an area or a person,¹³¹ for instance in cases relating to “[b]elligerent occupation and physical custody over detained individuals.”¹³² The capacity of a state to achieve incremental emission reduction does not imply any “effective control,” for instance, on the human rights impact of a heatwave occurring decades later in a different part of the world.¹³³ A few authorities continue to suggest an extension of the geographical scope of some treaty obligations, in particular with regard to the right to life, to situations where a state merely exercises “power” (not necessarily amounting to “effective control”) upon an individual's right in such a way as to affect that individual “in a direct and reasonably foreseeable manner”¹³⁴—but it is difficult to see how a state's capacity to achieve nominal reductions in global GHG emissions could constitute such power or affect individuals’ rights in any “direct” manner.

A 2017 advisory opinion of the Inter-American Court of Human Rights (IACtHR) on human rights and the environment pointed out that individuals whose rights are affected by transboundary environmental harm could be found to be under the effective control of the state of origin.¹³⁵ The Court, however, insisted that such extraterritorial application of human rights obligations is limited to “exceptional situations”¹³⁶ and occurs only where “there is a causal link between the act that originated in its territory and the infringement of the human rights of persons outside its territory.”¹³⁷ In other words, a state's failure to prevent transboundary environmental harm may, but does not necessarily, imply a breach of its obligation to protect human rights. For the human rights impact to be within the state's effective control, the causal link between the state's conduct and the human rights impacts must at the very least be significant, probably even relatively proximate, rather than remote and tenuous.¹³⁸ Thus, Walter Kälin and Jörg Künzli compare the advisory opinion with a case where a bullet had been shot at someone across an international border.¹³⁹ By contrast to what may happen in certain cases of direct transboundary environmental harm, there is no “smoking gun” (or factory) to blame for the impacts of climate change on human rights. As such, it is implausible that the impacts of climate change could ever fall within the effective control of a state—or that they could be considered the direct and reasonably foreseeable consequence of a state's conduct—on the sole ground of the state's ability to achieve marginal reductions in global GHG emissions.¹⁴⁰

There is no obvious possibility for the judicial interpretation of human rights treaties to evolve in ways that would apply human rights obligations to the global impacts of a state's GHG emissions. In many cases, a broad extraterritorial application would be irreconcilable with the text of human rights treaties whose geographical scope is explicitly limited to the state's “territory” or “jurisdiction.”¹⁴¹ These treaty provisions would be devoid of any effectiveness (effet utile)¹⁴² if every individual affected by the state's conduct was considered ipso facto within that state's “jurisdiction.” Even with regard to treaties without explicit jurisdictional limitation, such as the International Covenant on Economic, Social and Cultural Rights (ICESCR),¹⁴³ an extensive extraterritorial application of positive human rights obligations would be inconsistent with subsequent state practice:¹⁴⁴ states do not generally take the same measures to protect, for instance, the right to health beyond their territory as they do within it.¹⁴⁵ Thus, the authors calling for an extensive interpretation of extraterritorial jurisdiction generally “accept that States cannot be legitimately expected to be held accountable for all acts or omissions that somehow adversely affect the enjoyment of human rights by all individuals, anywhere in the world.”¹⁴⁶

2. “Collective Obligations”

Another line of argument suggests that, when approaching climate change mitigation as a human rights obligation, states must set their national interests aside and discharge their obligations as a group (i.e., the international community or the group of the parties to a treaty). Such a “collective obligation,”¹⁴⁷ if it is understood as an obligation held by a collective, is probably a contradiction in terms: only an (individual) legal person can incur an obligation and be held responsible for its breach.¹⁴⁸ No source or authority demonstrates the existence of a “collective obligation” of the international community as a whole or the parties to a treaty, as a single legal person, to protect human rights or to mitigate climate change.

The Supreme Court in Urgenda relied on a similar assumption when suggesting that the Netherlands, while unable to achieve globally significant mitigation outcomes on its own, had nonetheless to do its best. The Court asserted that the state's obligation to protect human rights is to be interpreted in light of a “joint responsibility” under the UNFCCC, which translates into a “partial responsibility” of the Netherlands to “do ‘its part’” in global mitigation action.¹⁴⁹ Regrettably, the Court did not specify the source of this “joint responsibility.” Climate treaties define collective objectives on climate change mitigation (e.g., the long-term goal of holding global warming “well below 2 °C” and to pursue efforts toward 1.5 °C)¹⁵⁰ and principles guiding burden-sharing (e.g., common but differentiated responsibilities and respective capabilities), but they do not impose any joint or collective obligations.¹⁵¹ These treaties require each party to take unspecified measures on climate change mitigation,¹⁵² not to “do its part” to ensure the achievement of the treaty's objective.¹⁵³ Nor can such an obligation arise from customary international law¹⁵⁴ or from subsequent practice in application of a treaty, for lack of consistent state practice: states, on their own admission, have not generally been communicating and implementing mitigation action consistent with the temperature targets included in the Paris Agreement.¹⁵⁵

John Knox appeared to envisage a comparable argument nested under human rights treaties when discussing their extraterritorial application. He suggested that “the states contributing most to the warming” could be considered to have effective control over “particularly extreme impacts [of climate change], such as the effect of climate change on small island states.”¹⁵⁶ For the reasons exposed above,¹⁵⁷ it is unlikely that an individual state would exercise “effective control” over the impacts of climate change. Knox may have been suggesting that a different conclusion could be reached if one considered the largest GHG emitters as a group, collectively holding an obligation to protect human rights. However, there is no evidence that human rights treaties create any such “collective obligation.”

Such arguments are often based on a misreading of the law of state responsibility. The applicants in Duarte Agostinho, a case currently pending before the European Court of Human Rights, refer to the Guiding Principles on Shared Responsibility to support their claim that states have a “shared responsibility” for the impacts of climate change on human rights.¹⁵⁸ Similarly, Margaretha Wewerinke-Singh relies on the concept of joint and several responsibility to invoke the obligation of a state to contribute to climate change mitigation.¹⁵⁹ Yet, neither the Guiding Principles on Shared Responsibility nor the concept of joint and several responsibility support the purported conclusions. The Guiding Principles seek to define the content of a state's responsibility when one or several other states are concurrently responsible for an internationally wrongful act; these Principles do not define primary obligations or any other of the conditions under which one or several states may initially be considered to be in breach of a primary obligation.¹⁶⁰ Likewise, the doctrine of joint and several responsibility, if applicable in international law at all, determines the consequences of a state's responsibility, not its existence.¹⁶¹

These arguments often converge toward Article 47 of the Articles on State Responsibility, which envisages the situation where several states are responsible for the same internationally wrongful act.¹⁶² However, the International Law Commission made it clear that Article 47 is only interested in the situation “where a single course of conduct is at the same time attributable to several states and is internationally wrongful to each of them,”¹⁶³ and that Article 47 does not constitute an exception to the principle of independent responsibility.¹⁶⁴ The Commentary thus notes that Article 47 does not apply ipso facto to situations “where several States by separate internationally wrongful conduct have contributed to causing the same damage,” for instance where “several States . . . contribute to polluting a river by separate discharge of pollutants.”¹⁶⁵ In such situations, the Commission adds, “the responsibility of each participating State is determined individually, on the basis of its own conduct and by reference to its own international obligations.”¹⁶⁶ Thus, nothing in the law of state responsibility extends to a group of states taken as a whole the obligation applicable individually to each of them.

3. Other-Regarding Obligations of Cooperation

It is only through international cooperation that global GHG emissions can be reduced in ways that benefit all.¹⁶⁷ This observation led Knox, in an influential report to the Human Rights Council, to point out that all states have an obligation to cooperate in addressing issues of international concern, as spelled out in particular under Article 55 of the UN Charter and the preamble to the UNFCCC.¹⁶⁸ This general international law obligation of cooperation, Knox suggests, “provides a framework for considering the application” of positive obligations on the protection of human rights in relation to climate change.¹⁶⁹ If a state must take the interests of other states into account, then, arguably, it must seek to mitigate climate change. Crucially, Knox considers this other-regarding¹⁷⁰ obligation of cooperation as one of “the human rights obligations of States in relation to climate change.”¹⁷¹ On this basis, Knox suggests that, under human rights law, states have “not only to implement current intended contributions, but also to strengthen those contributions to meet the [temperature] targets set out in article 2 of the Paris Agreement.”¹⁷²

Yet, while states certainly have an obligation to cooperate on climate change mitigation under general international law,¹⁷³ this obligation cannot readily be characterized as a “human rights obligation.” Article 55 of the UN Charter mentions “respect for, and observance of, human rights”¹⁷⁴ as one of the fields in which states must cooperate, but it does not—at least not expressly—create an obligation to cooperate on the protection of human rights.¹⁷⁵ If climate change mitigation falls within the ambit of the obligation of cooperation under the UN Charter, it is more convincingly under the first two paragraphs of Article 55: as either an issue affecting “standards of living . . . and conditions of economic and social progress and development,” or as the source of “international economic, social, health, and related problems.”¹⁷⁶

Overall, human rights treaties do not typically include any obligation of international cooperation. The few human rights treaties that mention “international assistance and cooperation” at all, like the ICESCR,¹⁷⁷ have often been construed as requiring states to consider receiving the international assistance and cooperation that they need—it is not clear whether these treaties create an obligation for states to provide assistance and cooperation when they can.¹⁷⁸ Even if they do, this obligation—which must be interpreted within the confines of subsequent state practice¹⁷⁹—surely does not amount to a full-fledged obligation for a state to protect economic, social, and cultural rights abroad in just the same way as it does within its own territory.¹⁸⁰

Knox suggests that a similarly broad obligation of cooperation may be inferred from any human rights treaty notwithstanding the absence of express provision. Recalling the obligation to perform treaties in good faith and its implication that every state must act “so as not to undermine the ability of other States to meet their own obligation,” he contends that the failure of states to cooperate on the mitigation of climate change would “prevent individual States from meeting their duties under human rights law.”¹⁸¹ Knox's observation relies on the doctrine of abuse of rights, which suggests that states must “abstain from acts calculated to frustrate the object and purpose and thus impede the proper execution of the treaty.”¹⁸² This doctrine has generally been envisaged as the source of an obligation not to act in a way that would defeat the object and purpose of the treaty; it is unclear whether it can also create an obligation to act in such a way as to enable the realization of the object and purpose of the treaty, especially one as open-ended and possibly as demanding as the obligation to cooperate could be.¹⁸³ Besides, although a state's failure to cooperate on the mitigation of climate change hinders the enjoyment of human rights, it does not impede other states from fulfilling their obligation to take appropriate measures to protect human rights.¹⁸⁴ In any case, a state's failure to cooperate on the mitigation of climate change is not “calculated” to prevent other states from complying with their human rights obligations.

States have a broad, other-regarding obligation of cooperation under general international law, but not under human rights treaties. This broad obligation of cooperation cannot be invoked by applicants under the same advantageous conditions as the obligation to protect human rights—in particular, it cannot be applied by treaty bodies or regional human rights courts. The next Section shows however that a narrower, inward-looking obligation of cooperation could be inferred from a state's obligation to protect the human rights of individuals within its territory or under its jurisdiction.

C. An Alternative Solution: An Inward-Looking Obligation of Cooperation

The obligation to protect human rights requires a state to take the “necessary steps” or, more broadly, to implement “appropriate measures,”¹⁸⁵ to protect the rights of individuals within its territory or under its jurisdiction. As shown above, a state's action on climate change mitigation, in itself, cannot be considered as a necessary or appropriate measure because it would result in virtually no benefit to the rights of individuals within that state's territory or under its jurisdiction;¹⁸⁶ in fact, such measure would rather undermine the rights of the individuals under the state's jurisdiction by placing a burden on them and on public resources.¹⁸⁷ By contrast, international cooperation could be an effective strategy—and therefore an “appropriate measure,” or even arguably a “necessary step”—for a state to protect the human rights of individuals within its territory or under its jurisdiction. By engaging in international cooperation or at least by “try[ing] to influence the international community,” a state can contribute to the realization of global mitigation outcomes which, over time, could bring in some real benefit for the enjoyment of human rights by individuals under its jurisdiction.¹⁸⁸

Human rights treaty bodies have sometimes construed the obligation to protect human rights as implying an inward-looking obligation of cooperation. For instance, the Human Rights Committee interpreted the obligation to protect the human rights of the child as implying that states must cooperate to ensure that every child has a nationality¹⁸⁹ and to facilitate family unity or reunification.¹⁹⁰ The application of a similar reasoning in relation to climate change mitigation is supported by the context in light of which human rights treaties are to be interpreted—states have repeatedly and emphatically recognized that climate change “calls for the widest possible cooperation by all countries.”¹⁹¹ Having recognized that climate change affects the enjoyment of human rights¹⁹² and that cooperation is essential to the mitigation of climate change, states have accepted that cooperation on climate change mitigation could be an appropriate measure to protect human rights. In contrast to other-regarding obligations of cooperation under general international law, this obligation derives from human rights treaties and, as such, it can be applied as part of these treaties. By analogy, the Federal Constitutional Court of Germany interpreted a constitutional provision on the right to life as requiring the state to seek a solution to climate change on the international plane.¹⁹³

A potential objection to the identification of this inward-looking obligation of cooperation is that a state's attempt to cooperate on climate change mitigation does not ensure that others will follow suit and, thus, that any tangible mitigation outcome will be achieved. In fact, cooperation by a given state is neither strictly necessary, nor sufficient, to ensure the realization of any mitigation outcome: efforts implemented by other states can always fill the gap. Instead of “wasting” scarce national resources in an attempt at triggering international cooperation—the objection goes—a state should rather pursue national priorities that are more directly effective for the protection of human rights, leaving it for other states to devise and implement mitigation action from which that state would benefit. This objection points out that free riding on other states’ mitigation action is a state's best possible strategy to protect the human rights of the individuals under its jurisdiction¹⁹⁴—unless, that is, other states follow the same reasoning.¹⁹⁵

This objection must be discarded because it relies on the impermissible premise that a state could (or should) attempt to deceive other states. The obligation to interpret and perform treaties in good faith¹⁹⁶ requires states to act in a “spirit of honesty”¹⁹⁷ and “to refrain from taking unfair advantage”¹⁹⁸ of others. This obligation precludes a state from seeking to free ride on mitigation action implemented by other states—to benefit from their action while avoiding their fair contribution to the costs.¹⁹⁹ This reasoning is confirmed by states’ call for cooperation²⁰⁰ and for equity²⁰¹ in responses to climate change. To comply in good faith with a treaty obligation to protect a human right, any given state must act in a way it considers fair and which would ensure, if other states followed the same precept, an optimal level of protection to the rights of everyone under that state's jurisdiction.

This implied obligation of cooperation does not require as much from states as the other-regarding obligation of cooperation that arises from general international law. The latter requires states essentially to set their national interests aside and to address international concerns in a spirit of global partnership by implementing their fair share of mitigation action.²⁰² Thus, when the general international law obligation of cooperation is applied to climate change, as Knox points out, it suggests that every state must contribute to climate change mitigation notwithstanding its own interest in mitigation outcomes.²⁰³ By contrast, the obligation of cooperation derived from human rights treaties requires a state to cooperate only if and inasmuch as international action contributes to the protection of the human rights of individuals within that state's territory or under its jurisdiction. If—for argument's sake²⁰⁴—a state were entirely immune from any impact of climate change, or otherwise able to manage all impacts affecting it through cost-effective adaptation measures, this state would not be bound to mitigate climate change under an inward-looking obligation of cooperation under human rights treaties, even though it would be bound to do so by other-regarding obligations of cooperation under general international law. As states are diversely exposed and vulnerable to the impacts of climate change,²⁰⁵ their inward-looking obligation of cooperation varies in intensity. The content of this inward-looking obligation depends on the right in relation to which it is invoked (e.g., rights to life, health, property, or livelihood) and on the foreseeable benefits of climate change mitigation for the protection of that right for individuals under the state's jurisdiction.²⁰⁶

To comply with this inward-looking obligation of cooperation, any state would presumably be expected at least to play a constructive role in international negotiations on climate change mitigation, facilitating rather than hindering the adoption of ambitious agreements. The inward-looking obligation of cooperation may also be interpreted as requiring that a state seek to limit or reduce GHG emissions within its territory, not for the sake of achieving nominal reduction in global GHG emissions, but as an integral part of global efforts on climate change mitigation. But a state with few GHG emissions within its territory or few realistic ways of reducing them could cooperate in other ways, for instance by providing financial or technical support to emission reduction activities conducted overseas. Regulating the importation or consumption of GHG-intensive goods and services, or even imposing sanctions on non-complying states, could also be appropriate measures to promote cooperation as long as these measures are compatible with other international law obligations.²⁰⁷

The implementation of this inward-looking obligation of cooperation on climate change mitigation is facilitated by the various procedures associated with human rights treaties. When applicants have standing to invoke a state's obligation to protect human rights before a national court,²⁰⁸ they would presumably also be allowed to invoke the implications of this obligation with regard to international cooperation. Likewise, treaty bodies could discuss compliance with these implied obligations in their concluding observations on national reports and general comments. Interstate dispute settlement mechanisms and advisory proceedings before regional human rights courts or human rights treaty bodies should also be able to implement these implied obligations.

IV. The Interpretation of Implied Mitigation Obligations

The previous Part demonstrated that, under human rights treaties, states have an inward-looking obligation of cooperation on the mitigation of climate change. The present Part explores how this implied mitigation obligation can be interpreted. In light of the principle of systemic integration, the interpreter of this implied mitigation obligation must take into account other relevant rules of international law, which could include general mitigation obligations arising from climate treaties²⁰⁹ and customary international law.²¹⁰ This, however, does not necessarily mean that compliance with an implied mitigation obligation requires compliance with its general mitigation obligations. This Part identifies and refutes a common assumption according to which human rights-based mitigation obligations incorporate general mitigation obligations in their entirety. It then advances an alternative theory according to which human rights treaties open only some “windows” onto general mitigation obligations. A human rights treaty requires a state to comply with general mitigation obligations, it is argued, only if and only inasmuch as justified by the protection of the treaty rights of individuals within its territory or under its jurisdiction.

A. Systemic Integration

The interpretation of human rights treaties generally follows the tenets of treaty interpretation, at least as a starting point.²¹¹ Among these tenets is the principle of systemic integration, which reflects the idea that a rule of international law must be interpreted within the context provided by other rules of international law.²¹² Article 31(3)(c) of the Vienna Convention on the Law of Treaties suggests that a rule must be “taken into account” in the interpretation of a treaty if this rule is (1) “relevant” and (2) “applicable in the relations between the parties.”²¹³

The condition of relevance is understood broadly: the referential rule “need have no particular relationship with the treaty other than assisting in the interpretation of its terms”;²¹⁴ it may have been adopted before or after the rule that is being interpreted.²¹⁵ For instance, the International Court of Justice in Gabčíkovo-Nagymaros held that a treaty on the implementation of a development project had to be interpreted in light of subsequent norms on the evaluation of environmental risks.²¹⁶ Thus, general mitigation obligations arising from climate treaties or customary international law are certainly relevant to the interpretation of the mitigation obligations derived from human rights treaties.

The second condition—the applicability of the referential rule “in the relations between the parties”—has also, oftentimes, been construed broadly, permitting reference to rules applicable to most, or even just to some of the parties to the treaty at issue, notwithstanding whether the referential rule was applicable to the parties to the dispute in relation to which the interpretation was taking place.²¹⁷ This broad approach to systemic integration suggests that any general mitigation obligation arising from climate treaties or customary international law should be taken into account when interpreting a human rights treaty as the source of an implied obligation on climate change mitigation. Some scholars, however, suggest a stricter approach to systemic integration, limiting reference to rules applicable to all parties to the treaty at issue.²¹⁸ This stricter approach could occasionally prevent the interpreter of some human rights treaties from taking climate treaties into account,²¹⁹ but it would not preclude references to customary international law. Either way, some general obligations on climate change mitigation, from climate treaties or at least from customary international law, are among the applicable rules that a court could take into account when interpreting a human rights treaty as the source of an obligation on climate change mitigation.

Human rights treaty bodies and regional courts have embraced the principle of systemic integration and, generally, they have followed a broad approach to it.²²⁰ For instance, the European Court of Human Rights in Loizidou highlighted that the ECHR “cannot be interpreted and applied in a vacuum”; rather, the interpreter must “take into account any relevant rules of international law.”²²¹ The Court found evidence of “common ground in modern societies” on the basis of poorly ratified treaties²²² and non-binding documents.²²³ Human rights treaties have been interpreted in light of other human rights treaties,²²⁴ treaties in other fields of international law²²⁵ (including environmental law treaties),²²⁶ and customary international law.²²⁷ The interest for systemic integration generally stems from the fact that it facilitates the adaptation of human rights treaties (as “living instruments”)²²⁸ to changing circumstances²²⁹ and provides judges with convenient benchmarks to interpret treaty rules that are otherwise “unclear or open-textured.”²³⁰ On the other hand, as Birgit Schlütter pointed out, this method creates a risk that human rights bodies could “go cherry-picking when determining the international rules that are held to govern a particular interpretation” of the treaty.²³¹

It is thus perfectly natural for the interpreter of an implied mitigation obligation to turn to the doctrine of systemic integration to determine the nature, scope, and content of these obligations. Accordingly, the Human Rights Committee suggested that the obligations of states “under international environmental law should . . . inform” the content of Article 6 of the International Covenant on Civil and Political Rights (ICCPR) on the right to life.²³² However, a line needs to be drawn between an interpretation of human rights treaties that is informed by—that is, takes into account—general mitigation obligations, and one that defers entirely to these general mitigation obligations. As the following shows, scholarship and judicial practice have failed to draw this line.

B. Refutation of the Incorporation Theory

The principle of systemic integration has generally been understood to suggest that, for a state to comply with a mitigation obligation implied from a human rights treaty, it must fully comply with all its general mitigation obligations. This incorporation theory has been tacitly accepted rather than carefully demonstrated. Closer scrutiny shows that it is inconsistent with the tenets of treaty interpretation.

1. Tacit Acceptance

The incorporation theory suggests that, if a human rights treaty implies a state's obligation to mitigate climate change, this obligation requires the state to fully comply with any obligation it has, under any source of international law, with regard to the mitigation of climate change. This theory has generally materialized in judicial practice and academic literature as a tacit assumption. Nonetheless, it has been instrumental, in particular, in national court decisions interpreting states’ human rights obligations as the source of an obligation to mitigate climate change.

Thus, the judgment of the Supreme Court of the Netherlands in Urgenda relied on the Vienna rule on systemic integration and the “common ground” method in European human rights law, according to which the interpretation of the ECHR must “[take] generally accepted standards into account.”²³³ On this basis, the Court asserted that, in order to comply with its obligation to protect the rights to life and to private and family life, the Netherlands had to comply with its customary law and climate treaty obligations²³⁴—which, in the Court's analysis, implied that the state had to reduce its emissions by 25 percent by 2020, compared with 1990.²³⁵ The Court thus largely followed the opinion of the procurator general, which called it to “base” its decision on customary international law.²³⁶

Similarly, the Supreme Court of Colombia ordered the state to comply with its international commitment to stop deforestation in order to fulfill its constitutional obligation to protect the rights to life, food, and a healthy environment by mitigating climate change.²³⁷ In doing so, the Court assumed that compliance with the former was a necessary condition for compliance with the latter.

The practice of treaty bodies reflects the same assumption. For instance, the Committee on the Rights of the Child recommended that Japan “reduc[e] its emissions of [GHGs] in line with its international commitments,”²³⁸ while the CESCR called on Norway to “intensify its efforts to achieve its [NDC] under the Paris Agreement.”²³⁹ These recommendations are admittedly of an ambivalent nature—treaty bodies do not generally distinguish between observations that interpret the state's legal obligations from those that are mere policy recommendations²⁴⁰—but they do reflect the prevailing understanding, on the part of these quasi-judicial bodies, that protecting human rights means complying with any and all norms on climate change mitigation, and that reviewing a state's compliance with its human rights obligations justifies a review of its compliance with general mitigation obligations.

In fact, quasi-judicial bodies have often implemented the incorporation theory along with an extensive interpretation of referential “rules”—including non-binding objectives. For instance, the CESCR suggested that the approval of fossil-fuel extraction projects ran against Ecuador's “commitments under the Paris Agreement,”²⁴¹ even though neither the Paris Agreement nor Ecuador's NDC define any commitment relating to fossil fuel extraction.²⁴² In another instance, the CESCR recommended that Norway take on more ambitious commitments on climate change mitigation than it already had within the climate regime.²⁴³ A joint statement by five treaty bodies asserted that states “must adopt and implement policies” aimed at realizing “the objectives of the Paris Agreement,”²⁴⁴ even though, as noted above, the treaty creates no obligation for states to realize its mitigation objectives,²⁴⁵ while state practice does not generally reflect acceptance of an obligation to adopt and implement mitigation action consistent with these objectives.²⁴⁶

Legal scholarship, likewise, has often assumed that, whenever a human rights treaty implies an obligation to mitigate climate change, it requires states, at least, to comply with any other treaty or customary obligation they have on climate change mitigation. For instance, Wewerinke-Singh suggests that the interpreter of human rights treaties should “consider international climate change law as providing minimum standards of protection” and hold “States to account for non-compliance with the standards they have set for themselves in domestic and international legal frameworks related to climate change.”²⁴⁷ She and Ashleigh McCoach welcomed the Court's application of the common ground approach in Urgenda as an “elegant way” of interpreting a specific benchmark that can be associated with open-textured human rights obligations.²⁴⁸ Similarly, Petra Minnerop and Ida Røstgaard assume that, if a mitigation obligation can be implied from Norway's constitutional obligation to protect the right to a healthy environment, and if this obligation can be interpreted in light of international law, then this obligation should be understood as requiring compliance with the state's general mitigation obligations under the UNFCCC.²⁴⁹ Boyd asserts that “[a] failure to fulfil international climate change commitments is a prima facie violation of the State's obligations to protect the human rights of its citizens.”²⁵⁰

Like treaty bodies, scholars have often suggested that human rights treaties should actually be interpreted as requiring more mitigation action than what states had accepted under climate treaties or customary international law. Paul Hunt and Rajat Khosla suggest that, to comply with their obligation to protect the right to health, in light of the impact of climate change on the enjoyment of this right, “states have a core obligation to take reasonable steps to stabilize [GHG] concentrations in the atmosphere at a level that prevents dangerous anthropogenic interference with the climate system,”²⁵¹ thus alluding to the “ultimate objective” of the UNFCCC²⁵² rather than to any particular “commitments” to which the parties had consented.²⁵³ Similarly, Knox asserts that the 1.5 and 2 °C temperature targets are “consistent with the obligations of States . . . to protect human rights from the dangerous effects of climate change”²⁵⁴—adding that each party to a human rights treaty must immediately strengthen its NDC in accordance with these temperature targets.²⁵⁵ Commenting on Knox's report, Boyle suggests that “[t]he UN special rapporteur is right in principle to argue that human rights law as a whole requires States to comply with expectations set out” by the mitigation objectives of the Paris Agreement.²⁵⁶ Boyle asserts that “human rights commitments could and should require States to implement Paris, and their record in doing so can and should be monitored and assessed by UN human rights bodies.”²⁵⁷

Yet, as Boyle himself concedes just a few pages earlier, “the argument that a policy which complies with the UN climate regime nevertheless violates the existing human rights obligation of States is not easy to make.”²⁵⁸ Boyle then turns to Knox's “more insightful approach,”²⁵⁹ but he does not explain how Knox, in his view, managed to make this uneasy argument. In a similar line, André Nollkaemper and Laura Burgers are skeptical of the analysis of the Supreme Court in Urgenda in that it blurs the “distinction between law and non-law”²⁶⁰—the 25 percent emission reduction target, after all, had only been mentioned (or rather alluded to) in non-binding party decisions.²⁶¹ But while Nollkaemper and Burger question the way the incorporation theory was implemented in Urgenda, they did not interrogate the theory itself. Neither Boyle nor Nollkaemper and Burger objected to the possibility for a court, when interpreting a human rights treaty as implying a mitigation obligation, to require the state to comply at least with any or all its obligations on climate change mitigation arising from any source.

2. Refutation

The problem with the incorporation theory is that it denatures the process of legal interpretation. Instead of merely taking general mitigation obligations into account to make sense of a human rights treaty, this theory overlooks the text as well as the object and purpose of the treaty at issue, focusing exclusively on general mitigation obligations.²⁶² Human rights treaties are thus reduced to a Trojan horse allowing extraneous rules and objectives to take hold of human rights institutions. When the incorporation theory operates, human rights treaties no longer pursue the objective of protecting the enjoyment of human rights, being instead entirely aimed at the mitigation of climate change.

The interpretation of a treaty should depend, among other things, on its text; its application, in turn, should take relevant, case-specific circumstances into account. Thus, Knox points out that “the content of the obligations of States to protect against environmental harm depends on the content of their duties with respect to the particular rights threatened by the harm.”²⁶³ Yet, similar conclusions will inevitably be reached, when applying obligations arising from various treaties recognizing different rights in diverse national circumstances, if one assumes—as Knox does—that, “[i]n applying their duty to protect against environmental harm that interferes with the enjoyment of human rights, . . . States must implement and comply with the standards that they have adopted.”²⁶⁴

This reasoning is incongruous. The obligation to protect the right to life, for instance, probably does not imply exactly the same mitigation obligation as the obligation to prevent discrimination against women, and these obligations should apply differently in states where the enjoyment of these rights is more or less exposed to climate impacts that mitigation action could avoid. To take an extreme example, the obligation of a state to protect the right of coalminers to an adequate standard of living may not necessarily imply the state's obligation to mitigate climate change at all, for closing coalmines—a measure that the state would likely take to mitigate climate change—would deprive the coalminers of their livelihood.²⁶⁵

This incongruity can be observed for instance, in Urgenda, by comparing the judgment of the District Court of the Hague with that of the Supreme Court. The District Court thought that it could not apply the ECHR in a public interest litigation;²⁶⁶ its judgment, instead, relies on the duty of care of the state under Dutch tort law. By contrast, the Supreme Court held that it could apply the ECHR in public interest litigations, and it relied exclusively on this substantive ground. Nevertheless, the two courts arrived at exactly the same conclusion. Furthermore, the Supreme Court made no difference between the impacts of climate change on the right to life on the one hand, and on the right to private and family life on the other hand, asserting that the state was expected to “take the same measures”²⁶⁷ pursuant to both rights. From whichever ground or angle they looked at the issue, the Dutch courts found that the state had to comply with its customary obligation on climate change mitigation, which they interpreted as requiring at least 25 percent emissions reduction by 2020 compared with 1990 levels.

However, there is no reason to assume that the mitigation obligation derived from the protection of the right to life involves exactly the same standard of care as the mitigation obligation derived from the right to private and family life does,²⁶⁸ or that these two obligations, in turn, are identical to the obligation that arises under the duty of care of the state under tort law. Rather, one would expect that the standard of due diligence applicable in relation to these various obligations would vary, in particular “according to the importance of the interest requiring protection.”²⁶⁹ A risk of interference with the right to life is arguably a more pressing consideration than a risk of interference with the right to private and family life; and the duty of care arguably allows broader consideration for the need for mitigation action as it relates not only to the enjoyment of human rights, but also of human welfare in general. The two courts arrived at the same conclusion because, while claiming to apply tort law or European human rights law in light of customary international law,²⁷⁰ they were, in fact, applying customary international law.

The incorporation theory is problematic because it allows judges to bypass rules on jurisdiction and admissibility. The applicants in Urgenda had standing to invoke the duty of care of the state and its obligation to protect human rights, but not its customary international law obligations.²⁷¹ Likewise, treaty bodies and regional human rights courts have jurisdiction to interpret human rights treaties, but not to apply general mitigation obligations arising from climate treaties or customary international law. Systemic integration provides no justification for overlooking the absence of state consent to jurisdiction with regard to the application of the referential rule.²⁷²

Questions about the implications of the principle of systemic integration for a court's jurisdiction are not entirely new or specific to climate change mitigation. Judge Buergenthal accused the International Court of Justice in Oil Platforms of using this principle “to apply international law on the use of force simply because that law may also be in dispute between the parties before it and bears some factual relationship to the dispute of which the Court is seised.”²⁷³ The Court firmly denied doing so.²⁷⁴ Subsequently, in Pulp Mills, the Court stated in the clearest possible terms that systemic integration had “no bearing on the scope of the jurisdiction conferred on the Court”²⁷⁵ and, accordingly, that Argentina could not claim the application of general international law under the pretense of interpreting the treaty under which the Court had jurisdiction. Consistently, the Court held in Jadhav that its jurisdiction to interpret and apply the Vienna Convention on Consular Relations allowed it to take the ICCPR into account, but not to apply it by entertaining claims of human rights violations per se.²⁷⁶

Thus, the principle of systemic integration does not justify a monolithic application of international law where a court, having jurisdiction to interpret a treaty, could apply any related rule of international law. Richard Gardiner's guide to treaty interpretation highlights the distinction to be drawn, under Article 31(3)(c) of the Vienna Convention on the Law of Treaties, “between using rules of international law as part of the apparatus of treaty interpretation and applying the rules of international law directly to the facts in the context of which the treaty is being considered.” As Gardiner points out, “[t]he former is within the scope of the Vienna rules, the latter is not.”²⁷⁷ Alexander Orakhelashvili, likewise, notes that “the purpose of interpreting by reference to ‘relevant rules’ is . . . not to defer the provisions being interpreted to the scope and effect of those ‘relevant rules,’ but to clarify the content of the former by referring to the latter.”²⁷⁸ International courts and tribunals have consistently recognized that every rule has a “separate existence” even when several rules point to the same direction or are expressed in similar terms.²⁷⁹ Thus, taking general mitigation obligations into account to interpret human rights treaties does not justify the incorporation of the former into the latter.

C. An Alternative Theory: Windows of Applicability

1. The Theory

An obligation on the mitigation of climate change that derives from a human rights treaty is to be interpreted based on the terms of the treaty from which it is implied, its context, and its object and purpose.²⁸⁰ Its interpreter is to take general mitigation obligations into account together with the context of the treaty, in light of the principle of systemic integration,²⁸¹ but without deferring to these general mitigation obligations.

The terms of human rights treaties and their objects and purposes generally allow consideration for the benefits of international cooperation on climate change mitigation with regard to the enjoyment of human rights,²⁸² but these treaties are not interested in the broader benefits of climate change mitigation for human welfare, the interests of future generations, and the protection of nature per se.²⁸³ By contrast, general mitigation obligations arising from climate treaties or customary law take at least some of these broader benefits into account. States’ general obligations arising under climate treaties²⁸⁴ pursue the ultimate objective of preventing “dangerous anthropogenic interference with the climate system,”²⁸⁵ a phrase which invites consideration for an open-ended list of values, among which climate treaties highlight sustainable development,²⁸⁶ food security,²⁸⁷ ecological integrity,²⁸⁸ and intergenerational equity,²⁸⁹ among other things.²⁹⁰ On the other hand, customary international law requires states to exercise due diligence to protect the various rights of other states (e.g., the right to exploit natural resources),²⁹¹ including their right to protect the rights of their citizens.²⁹² As human rights treaties only take into account some of the benefits of climate change mitigation that inform general mitigation obligations, human rights treaties only require a part of the mitigation action that states must implement under their general mitigation obligations.

This Article uses the metaphor of a windows to suggest that a state's obligation to protect a human right of individuals within its territory or under its jurisdiction provides only, at most, a limited opportunity to take the benefits of climate change mitigation into account, hence, to apply general mitigation obligations. For a state to comply with an implied mitigation obligation, it only needs to comply with the part of its general mitigation obligations that can be sighted through the window that the human rights treaty opens onto these general mitigation obligations. The size of this window of applicability—that is to say, the content of implied mitigation obligations, for instance in terms of a standard of due diligence²⁹³—is contingent on the treaty, the right, and the national circumstances.²⁹⁴ More specifically, windows of applicability depend on the following four variables.

Variable 1: The personal scope of the treaty. Some human rights treaties protect the rights of everyone within the state's territory or under its jurisdiction; other treaties protect only a specific category of population.²⁹⁵ All other things being equal, general human rights treaties justify more ambition on climate change mitigation than specific human rights treaties because the former perceive the benefits of climate change mitigation for a larger population than the latter do.²⁹⁶ For instance, the obligation to protect the right to life under the ICCPR (where it applies to the entire population within the state's territory and under its jurisdiction) requires more ambitious mitigation action than the obligation to protect the same right under the Convention on the Rights of the Migrant Workers (where it applies only to a subcategory of the same population).²⁹⁷

Variable 2: The relative importance of the right. Despite the absence of formal hierarchy among rights,²⁹⁸ more weight is generally attached to the protection of certain rights, in particular the rights that cannot be derogated to even in case of emergency (e.g., the right to life), as these rights often constitute a necessary condition for the effective enjoyment of other rights.²⁹⁹ States are held to a higher standard when protecting objectives to which a higher value is attached:³⁰⁰ they are expected to invest more resources to prevent a potential interference with the right to life, for instance, than they are to prevent an interference with the right health, if only because the enjoyment of the former is a necessary condition for the enjoyment of the latter. Thus, all other things being equal, a state's obligation to protect the right to life commands greater ambition on climate change mitigation than its obligation to protect the right to health.

Variable 3: The potential benefits of climate change mitigation for the protection of the right within the state's territory or under its jurisdiction. Human rights treaties require states to mitigate climate change only as a way to protect the enjoyment of the rights that they have to protect. The benefits of climate change mitigation for the enjoyment of a right depend on national circumstances—the population's exposure and vulnerability to the impacts of climate change³⁰¹ and the likelihood that climate change mitigation may alleviate these impacts. For instance, the content of the mitigation obligation that can be inferred from a state's obligation to protect the right to food depends on whether climate change would likely affect food security within the state, and also on whether successful mitigation action remains capable of reducing this impact. In general, the rights to life and health would likely be severely affected in developing countries,³⁰² whereas developed countries are more exposed to economic loss,³⁰³ which could be framed as an interference with the right to property. Where it is recognized, the right to a healthy environment could also justify relatively broad mitigation obligations, although it remains unable to account for all the impacts of climate change on human welfare, future generations and ecological resources.³⁰⁴

Variable 4: The potential unintended consequences of mitigation action for the enjoyment of treaty rights within the state's territory or under its jurisdiction. A state's obligation under a human rights treaty can justify mitigation action only to the extent that the benefits of mitigation action for the enjoyment of treaty rights prevail over its unintended consequences. This observation calls, in particular, for considering the state's capacity to mitigate climate change without hindering other priorities instrumental to the protection of the rights of individuals within its territory or under its jurisdiction (e.g., economic development, poverty eradication, or climate change adaptation).³⁰⁵ As such, developing countries may generally be held to a lower standard on climate change mitigation under their human rights treaty obligations, to the extent that they may not be able to invest in ambitious mitigation action without hindering the pursuance of these other priorities.³⁰⁶

On the basis of these four variables, the windows-of-applicability theory provides for an interpretation of implied mitigation obligations in line with the tenets of treaty interpretation. This theory reflects the terms as well as the object and purpose of human rights treaties by requiring a state to mitigate climate change only if and inasmuch as this contributes to the effective protection of the treaty rights. The theory also takes the context of application into account, acknowledging that not every right has the same implications for climate change mitigation in every country.

2. Applications

A few illustrations can help to explain the ramification of the windows-of-applicability theory when compared with the incorporation theory. Applied to Urgenda, for instance, the windows-of-applicability theory would have attached great weight to the fact that the Netherlands is particularly exposed to life-threatening impacts of climate change³⁰⁷ and to its large financial capacity, in light of variables 3 and 4.³⁰⁸ Moreover, if the Supreme Court of the Netherlands had followed the windows-of-applicability theory, it would have distinguished the implications of the right to life from those of the right to private and family life as variables 2 and 3 apply differently in relation to these two rights. The Court's interpretation of the right to life as implying a far-reaching mitigation obligation is not entirely implausible given the fundamental importance that the ECHR attaches to this right and the benefits that international cooperation on climate change mitigation could bring to its enjoyment within the territory of the Netherlands; the Court's identical interpretation of the right to private and family life is less convincing.³⁰⁹

Overall, if the Supreme Court of the Netherlands had followed the windows-of-applicability theory, it would not have assumed that the state's obligation to protect either of these rights requires full compliance with its general mitigation obligation (e.g., under customary international law).³¹⁰ An obligation to protect the right to life, or a fortiori the right to private and family life, does not justify as much mitigation action as the general mitigation obligations that the state accepted in light of a broader consideration of the impacts of climate change. An unusual degree of judicial discretion would then, unavoidably, have been involved in assessing the precise level of mitigation action implied by obligation of the Netherlands to take appropriate measures to protect these two rights. The judges could of course have concluded that, while the human rights treaty implies a far-reaching mitigation obligation, the state was already acting consistently with this obligation.³¹¹ In fact, if the “common ground” method is taken seriously, it should be expected that most states would, most of the time, be found to be acting in compliance with their obligation. Thus, the Court in Urgenda would likely, but not necessarily, have found that the Netherland's preexisting policies and actions on climate change mitigation were sufficiently ambitious to be consistent with its obligation to protect the right to life. By contrast, as far as the right to private and family life is concerned, a finding of compliance would have been virtually unescapable.

As the windows-of-applicability theory recognizes the relevance of national circumstances, it is suspicious of any attempt to transplant Urgenda to other countries. In one of the first attempts to do so, the applicants in Natur og Ungdom failed to provide any evidence that climate change would significantly affect either the right to life or that of private and family life within Norway's territory or under its jurisdiction.³¹² As such, the Supreme Court of Norway justly—at least on the basis of the parties’ submissions—dismissed the applicants’ submission that a far-reaching mitigation obligation could be implied from Norway's obligation to protect these rights.³¹³ Likewise, the windows-of-applicability theory provides a skeptical outlook on the applicants’ contention, in Duarte Agostinho, that the thirty-three high-income member states of the Council of Europe must enhance their ambition on climate change mitigation in order to comply with their obligation to protect the rights to life and to private and family life.³¹⁴ The interpretation of the ECHR proposed by the applicants is certainly not supported by state practice, and it does not constitute a common ground among the member states of the Council of Europe, if—as the applicants contend—none of the thirty-three respondent states complies with it.

Overall, the windows-of-applicability theory suggests that human rights treaty bodies do not all have a role to play in promoting mitigation action. On the one hand, there is no denial that the Human Rights Committee and the CESCR may be able to interpret the obligation of some states to protect some rights under, respectively, the ICCPR and ICESCR, as implying substantive mitigation obligations, given in particular the broad personal scope of these treaties and the potential benefits of climate change mitigation for the enjoyment of these rights in many countries.³¹⁵ On the other hand, the Convention on the Elimination of All Forms of Discrimination against Women, the Convention on the Rights of Persons with Disabilities, and the Migrant Workers Convention do not easily lend themselves to such interpretations: their personal scope is more limited and (by contrast to the Convention on the Rights of the Child) the rights that these treaties protect are not uniquely affected by the impacts of climate change.³¹⁶ For instance, even though climate change may have different impacts on men and women,³¹⁷ climate change mitigation is unlikely to be a particularly effective way to fight against discrimination against women.³¹⁸

3. Discussion

The windows-of-applicability theory results in a complex but nuanced interpretation of human rights treaties as the source of an obligation on climate change mitigation. On the one hand, this theory does not categorically exclude the possibility of interpreting human rights obligations as implying an obligation to mitigate climate change. Compliance with human rights treaties requires a state to implement mitigation action to the extent that this may effectively promote the enjoyment of the treaty's rights within the state's territory or under its jurisdiction. This interpretation would most likely be arrived at in relation to general human rights treaties, rights of a fundamental importance (such as the right to life), and states whose population is particularly likely to benefit from mitigation action without being adversely affected by its unintended consequences. In this sense, Urgenda provided a relatively strong case for the recognition of a mitigation obligation under a human rights treaty in relation to the right to life.

On the other hand, this theory opposes the use of human rights treaties as a Trojan horse at the service of climate change mitigation. Human rights treaties are not a back door for judges to impose on states the obligations on climate change mitigation that states have never accepted;³¹⁹ nor can human rights institutions be transformed into substitutes for the full-fledged compliance mechanism that states decided not to create under the Paris Agreement.³²⁰ This theory thus challenges any suggestion that human rights law “may secure higher standards” on climate change mitigation than general mitigation obligations do.³²¹ Windows of applicability are always relatively narrow because many of the impacts of climate change that general mitigation obligations seek to avoid cannot be framed as human rights impacts. It remains however that the impacts of climate change are arguably so severe that even a narrow window of applicability could conceivably allow a judge to raise serious concerns for the protection of human rights and to infer relatively far-reaching mitigation obligations—but the argument is neither obvious nor easy to make, and it can unfold successfully only in very specific national circumstances.

There is no denial that the windows-of-applicability theory is particularly difficult to implement. A judge can certainly not fully rely on any objective method to assess and weigh the four variables relevant to determining the size of a window of applicability. In particular, there is no generally accepted or objective way of measuring or comparing a state's vulnerability to climate change,³²² let alone the benefits of climate change mitigation for the protection of a right. Surely, the difficulty of interpreting the law does not normally release a judge from her duty to adjudicate.³²³ Nor should this difficulty necessarily lead to an extension of the deference that judges show to policy decisions³²⁴—to the contrary, one could argue that the risk of widespread impacts on fundamental rights justifies closer judicial scrutiny. What precisely a state must do to comply with its implied obligation to cooperate on climate change mitigation under a specific human rights treaty and in relation to a particular right, or what precisely it must do in order to comply with its general mitigation obligations under the UNFCCC and under customary international law, are not questions that can be answered with mathematical accuracy, but they may nevertheless be judicial questions.

V. Conclusion

Human rights treaties may be interpreted as requiring a state to cooperate on climate change mitigation in good faith to the extent that this helps to protect the rights of individuals within its territory or under its jurisdiction. This implied mitigation obligation allows the interpreter of human rights treaties to open a window onto general mitigation obligations arising from climate treaties and customary law. Yet, this window is generally narrow: as human rights treaties do not fully take into account the broad benefits of climate change mitigation on human welfare, the interests of future generations, and the protection of nature per se, they do not require full compliance with general mitigation obligations. The size of a window of applicability—that is to say, how far a human rights treaty requires a state to comply with its general mitigation obligations—depends on the personal scope of the treaty and the importance of the right at issue, as well as the potential benefits of climate change mitigation for the enjoyment of the right, and its unintended consequences for the enjoyment of rights, within the state's territory or under its jurisdiction.

This analysis thus suggests that human rights treaties may have a rather limited role to play with regard to climate change mitigation.³²⁵ In fact, the interpretation of human rights treaties as the source of mitigation obligations faces some of the major hurdles that have hindered international cooperation on climate change mitigation in the last three decades. For one thing, human rights treaties view nature mostly in instrumental terms, and largely ignore the interests of future generations. Overall, international human rights law encourages each state to protect the rights of individuals within its territory rather than to cooperate on the global common good. This inherent tension between national interests and international cooperation will not be solved through an incremental extension of international human rights law, be it through the recognition of new rights (e.g., to a healthy environment or a sustainable climate),³²⁶ the identification of fictitious rights-holders (e.g., “future generations” or “Mother Earth”),³²⁷ or the extension of the extraterritorial application of human rights treaties—not, that is, without betraying the text, and the object and purpose, of human rights treaties, and using them as a Trojan horse at the service of extraneous objectives.