Necessity plays a significant role in any legal system as unpredictable or extraordinary situations can require the adoption of measures departing from the normally applicable law in order to protect basic values and fundamental interests. International law is not an exception. The admissibility of the adoption of measures on grounds of necessity has been accepted by international courts and tribunals, in state practice, including international conventions, as well as in doctrine.

This chapter examines the relevance of the principle of necessity to the international rules on the use of force. It claims that necessity has been the source of the international rules on the use of force which as independent titles manifest themselves in institutional as well as in customary forms. It also claims that the use of force constitutes a special regime of international law which is distinct from the law of state responsibility with which it however interacts.

Necessity performs two distinct functions in the Law of Armed Conflict. In a wider sense, it stands as a restraining principle of LOAC, permitting the use of legally regulated violence only to the extent necessary to achieve the aims of war. In a narrower sense, it operates as a circumstance precluding wrongfulness, enabling a belligerent to perform some acts that, as a rule, would be prohibited. As far as the general principle of restraint is concerned, the main debate presently regards the definition of military objective and the requirement of definite military advantage, while the permissive function of necessity in armed conflict mainly displays its effects with regard to obligations related to the protection of (public, private, cultural) property. In International Criminal Law, the plea of military necessity (or of ‘the necessities of the conflict’) should only justify actions undertaken by a responsible actor after a wary evaluation of the situation in the battlefield. The plea of duress, where the accused argues that in committing the acts complained of, he/she acted under an immediate threat, should be accepted with more flexibility. As concerns State Responsibility, a critical issue is represented by the relationship between military necessity and the use of force. While jus in bello must always be applied equally by belligerents, states must respect the requirements of self-defence in order to be regarded as acting lawfully under jus ad bellum. However, the legality of the use of force is irrelevant in the area of individual criminal responsibility. Those who are engaged in an armed conflict are not concerned with its legality and therefore their behaviour must be exclusively judged on the basis of the standard prescribed by LOAC.

As far as the topic of ‘necessity and human rights’ is concerned, considerations informed by necessity mainly play a role as grounds for restricting or derogating from human rights on the basis of primary norms contained in international human rights treaties, rather than on the basis of the secondary necessity norm set out in Article 25 of the ILC Articles. The arguably exhaustive treatment of necessity-informed restrictions and derogations in those treaties largely precludes invocation of the general defence of necessity under the law of State Responsibility. Indeed, the drafters have already factored in necessity when drafting human rights treaties. In so doing, they have incorporated necessity into the law itself as a justification for limitations to human rights, thereby excluding reliance on a broader concept of necessity outside this framework. Beyond the human rights treaties, for that matter, States are very hesitant to invoke necessity as an excuse, as this would amount to admitting that their conduct was in fact unlawful (although excusable). Apart from that, ‘human rights’ may possibly qualify as an ‘essential interest’ excusing non-compliance with non-human rights related international law obligations, but it can be said that the notion of jus cogens may be a more potent tonic to set aside ‘incompatible’ lesser norms of international law.

This article focuses on the management of circumstances of calamity generally in IEL, as well as calamity as a necessity in international economic relations in the framework of State Responsibility. The focus on calamity as a necessity defence to State Responsibility is however from a ‘necessity paradigm’—i.e., from the view point of responding effectively to circumstances of calamity, which call for a necessary response, wherein the calamity is the centre of focus. This is in contrast to the stand-point of State Responsibility wherein honouring State Responsibility is central and informs the response to the necessity circumstance (the ‘State Responsibility paradigm’). The necessity paradigm of calamity is grounded mainly on justice and development imperatives, along with the conclusion that the State Responsibility paradigm can be incomplete in its response to the calamity; as well as incoherent from the perspective of the world economic order as a whole. The general focus on calamity in International Economic Law adopted here is with specific reference to its key spheres viz., international monetary and financial law within the framework of the IMF; international trade in the context of the WTO; International Development Law, particularly with reference to international investment practice; and finally with an examination of global economic crisis management.

A number of investment cases in the aftermath of the Argentine economic crisis 2001/2002 have addressed important issues of state of necessity. The tribunals affirmed that the codification of this defence in the 2001 ILC Articles on State Responsibility largely reflects customary international law and they rejected the argument that the highly complex nature of necessity characterized it as a non-justiciable political question. ICSID and other tribunals have also concurred on some crucial aspects of the necessity defence, like the potential qualification of economic emergencies as necessity situations or the fact that necessity can be invoked only in extreme cases. Nevertheless, the application of these principles to the actual situation in Argentina led to divergent and partly conflicting outcomes. After assessing the relationship between derogation clauses contained in many investment treaties and state of necessity this contribution focuses on specific aspects which entitle a State to invoke necessity as a ground for not fulfilling its obligations. It pleads for a proportionality approach in determining whether the actual measures adopted should be regarded as the only means to safeguard State interests. Similarly, it supports a nuanced assessment concerning the contribution element by requiring that it be substantial.

This essay investigates the institution of necessity in international environmental law. The point of departure is the analysis of Article 25 of the International Law Commission (ILC) Articles on State Responsibility regarding its applicability to the particular field of international environmental law. The special feature of the plea of necessity in international environmental law is that it has developed through the case-law. Without doubt, the plea of necessity can be invoked in international environmental law. However, (as in other areas of international law), it remains an exception. This was confirmed by the International Court of Justice which made clear that the invocation of necessity is very problematic. There are some unresolved issues concerning the plea of necessity in international environmental law, such as the question of the precautionary principle. The inclusion of the precautionary principle in the concept of necessity appears to give rise to a certain degree of difficulty, mainly deriving from the seemingly irreconcilable requirements of the ‘imminence of peril’ and scientific uncertainty represented by the precautionary principle. In the view of the present author, the complex and exceptional legal character of necessity in general and as applied in international environmental law in particular, will deter States from invoking it; therefore, the available practice will remain very scarce and to a certain degree inconclusive, as has already been evidenced by the available case law, analyzed in this essay.

This article discusses how the EU legal order deals with cases where Member States deem that the principle of necessity justifies a deviation from EU law. It analyses the various exceptional clauses laid down in primary and secondary EU law, and discusses the tensions which their application may raise in the context of the Union's idiosyncratic constitutional order. It assesses the broad powers with which national courts are endowed, and highlights the dynamic nature of the Union's approach to accommodating potential deviations. Finally, it focuses on an area at the core of national sovereignty, namely defence, and outlines the gradually shifting approach to its economic aspects which the Union institutions have developed over the years.