The Use of Earth Observation Tools for the Surveillance and Enforcement of Marine Protected Areas on the High Seas

Abstract

In the aftermath of the adoption of the Implementing Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biodiversity in Areas Beyond National Jurisdiction (BBNJ Agreement) and in view of the global target to protect at least 30 per cent of the ocean by 2030 (30×30), an issue that merits attention is the surveillance of marine protected areas (MPAs) on the high seas. The BBNJ Agreement is remarkably silent on how the relevant management measures in future MPAs will be implemented, despite the fact that enforcement challenges are prevalent in existing MPAs. This article discusses the potential use of maritime domain awareness (MDA) tools, including earth observation tools like satellites, in ensuring effective surveillance and subsequent enforcement of high seas MPAs. The article first introduces the concept of MDA and the use of earth observation tools in that context, highlighting the advantages that such tools may have in ensuring compliance in MPAs. It then explores the legal framework governing the employment of earth observation tools in high seas MPAs. The article argues that States are not merely permitted but also obligated to monitor their vessels’ activities in high seas MPAs. Furthermore, States are under a general obligation of cooperation, including the obligation to share information that is obtained by MDA tools. Finally, the article briefly discusses how evidence, like satellite imagery, could be used for enforcement purposes, including before domestic courts. It concludes that the use of earth observation tools would be instrumental to the effective surveillance and enforcement of high seas MPAs.

1. Introduction

Areas Beyond National Jurisdiction (ABNJ), which comprise the high seas and the international seabed, make up 64 per cent of the oceans and seas and play an essential role in conserving marine living resources and biological diversity. ¹ In this context, the use of marine protected areas (MPAs) as an integrated area-based management tool (ABMT) to regulate human activities and thus conserve biodiversity in ABNJ, has attracted increasing attention from the international community. ²

Notwithstanding the significance of ABMTs for protecting vulnerable marine ecosystems, ³ there is no central guidance under the United Nations Convention on the Law of the Sea (UNCLOS) ⁴ on their use, merely a series of fragmented and sectoral approaches. ⁵ Having acknowledged this gap in the protection of Marine Biodiversity in ABNJ, the Ad Hoc Open-ended Informal Working Group on Marine Biodiversity in ABNJ agreed in 2011 that ABMTs would be included in the ‘package deal’ to be addressed by a new Implementing Agreement under UNCLOS on the Conservation and Sustainable Use of Marine Biodiversity in Areas Beyond National Jurisdiction (BBNJ Agreement). ⁶ The BBNJ Agreement was finally adopted on 19 June 2023, ⁷ after long and arduous negotiations, ⁸ and is set to enter into force on 17 January 2026. ⁹ Having as one of its overriding aims the conservation of priority protection areas through the establishment of a comprehensive system of ABMTs, the adoption of the BBNJ Agreement marks a significant milestone towards the protection of marine biodiversity and a vital step towards achieving the Convention on Biological Diversity Kunming-Montreal Global Biodiversity Framework’s goal of protecting at least 30 per cent of marine habitats by 2030. ¹⁰

One of the principal achievements of the BBNJ Agreement is that it provides a global and cross-sectoral legal basis for the designation of MPAs in all marine ABNJ and across all sectors of human activities. ¹¹ Also, the BBNJ Agreement offers a definition of MPA, something that to date has been missing from international law. ¹² An MPA, for the purposes of the BBNJ Agreement, ‘means a geographically defined marine area that is designated and managed to achieve specific long-term biological diversity conservation objectives and may allow, where appropriate, sustainable use, provided it is consistent with the conservation objectives’. ¹³

Given the prominence of MPAs for the protection of marine biodiversity, one would expect that the BBNJ Agreement would have included detailed provisions on their implementation. Quite to the contrary though, the BBNJ Agreement sets forth only a general obligation for States Parties to ‘ensure that activities under their jurisdiction or control that take place in areas beyond national jurisdiction are conducted consistently with the decisions adopted under this Part’. ¹⁴ In addition, Article 26 stipulates that ‘[p]arties shall, individually or collectively, report to the Conference of the Parties on the implementation of area-based management tools, including marine protected areas, established under this Part and related measures’. ¹⁵ Apart from this reporting duty, there is no other mechanism for ensuring compliance with and enforcement of the BBNJ Agreement. It is thus uncertain how the effective implementation of the MPAs, or even the BBNJ Agreement itself, will be secured. ¹⁶ One option would be for measures concerning monitoring and implementation of MPAs to be set out in relation to a specific MPA as part of the proposed management plan submitted by the States Parties and decided by the Conference of the Parties (COP). Alternatively, such measures could form part of a decision or recommendation subsequently adopted by the COP on the implementation of the BBNJ Agreement. ¹⁷

These measures could include, among others, ¹⁸ the use of modern technologies, such as radars or satellites, for monitoring, control and surveillance (MCS) of MPAs. ¹⁹ Indeed, such tools are attaining increasing significance in providing for efficient Maritime Domain Awareness (MDA). ²⁰ MDA is already instrumental to the fight against transnational organised crime at sea, ²¹ but can also provide, for present purposes, an important mode of MCS of MPAs. Apart from their paramount importance in reporting and raising awareness, earth observation tools, particularly satellite images, have significant evidentiary value in establishing the commission of illicit acts within MPAs. ²²

There are already a number of high seas MPAs designated mainly by Regional Seas Arrangements: ²³ eight in the North East Atlantic under the Convention for the Protection of the Marine Environment of the North East Atlantic (OSPAR Convention); ²⁴ two in the Southern Ocean established by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR); ²⁵ and one in the Mediterranean Sea under the Protocol to the Barcelona Convention Concerning Specially Protected Areas and Biological Diversity in the Mediterranean (SPAMIs Protocol) (Pelagos Sanctuary). ²⁶ ABMTs, in the form of high seas bottom fishing closures, have also been designated by Regional Fisheries Management Organisations (RFMOs). ²⁷ However, none of these MPAs systematically employ MDA tools for their surveillance and enforcement.

It is thus the purpose of this article, first, to demonstrate the utility of the use of earth observation tools for surveillance and enforcement of high seas MPAs and, second, to explore the legal framework governing the use of such tools for the said purposes, in particular the relevant rights and obligations of States in this regard. The article starts by introducing the concept of MDA and the use of earth observation tools in that context, highlighting the advantages that such tools may have in ensuring compliance in MPAs (Section 2). It then discusses whether States are permitted, or even obligated, to use such tools in relation to their vessels in high seas MPAs (Section 3). Next, it explores whether States are permitted to use such tools to monitor the activities of foreign-flagged vessels in high seas MPAs, and what measures can they take upon identifying an illegal activity therein (Section 4). Finally, it addresses the potential use of satellite data for enforcement purposes (Section 5). Section 6 concludes that the use of earth observation tools would be instrumental to the effective surveillance and enforcement of high seas MPAs.

2. MDA and earth observation tools in high seas MPAs

2.1. The concept of MDA

The concept of MDA is not included in UNCLOS; it arose in the context of increased maritime security concerns after the events of 9/11 in the United States and the ensuing fears about the potential impact of terrorist attacks on global trade if the maritime industry were targeted. ²⁸ According to the definition provided by the International Maritime Organization (IMO), MDA is ‘[t]he effective understanding of any activity associated with the maritime environment that could impact upon the security, safety, economy or environment’. ²⁹ Intelligence-gathering and information-sharing at sea are critical for ensuring maritime security. ³⁰ In this light, MDA aims to provide an ample database of information, often in real time, against which maritime security activities—including interceptions of vessels at sea—can be planned and implemented, through centralised data-mining techniques. ³¹ In other words, MDA policies are an indispensable tool to gather and share information on who does what and where at sea. ³²

The task of intelligence-gathering is particularly challenging in the maritime environment, ³³ specifically with respect to large maritime areas, including MPAs on the high seas, since conventional assets like warships, coastguard vessels and State aircrafts or even drones lack the operational capacity for continuous and effective surveillance of such areas. ³⁴ In this regard, an array of modern technologies have emerged over recent decades to facilitate MDA.

2.2. Earth observation tools

MDA policies and practices are heavily based on available technology. In view of rapid technological advancements, MDA tools have become more sophisticated over time. In an earlier era, MDA tools included oceanographic, marine geological, geophysical, chemical, biological and acoustic data and the use of equipment such as fathometers, swath bottom mappers etc. ³⁵ Today, MDA tools may range from surface vessels and submarines, as well as remotely operated vehicles, autonomous underwater vehicles (AUVs) and seabed landers to satellites and radars. ³⁶ Such MDA tools are prone to evolve in the future requiring an adaptive legal framework. Some of the most commonly used tools for MDA are as follows.

2.2.1. Vessel Monitoring Systems (VMS)

VMS is a ‘co-operative’ satellite-based system that monitors participating vessels. ³⁷ Vessels using VMS must carry an operating a transmitter or transceiver, which sends the position of the vessel to the competent authorities of the flag State. Thus, VMS provides monitoring agencies with accurate locations of participating vessels at periodic time intervals. In fact, VMS has been a crucial tool for managing national and regional fisheries, as they provide a reliable source of vessel position and catch data. Indeed, they are generally mandated by coastal States or RFMOs. ³⁸ Commercial fishers must have a VMS system as part of the licensing process by the flag State, the coastal States (as part of access conditions) and/or the RFMO(s) under which the vessel is to fish. However, the flag State or RFMO concerned owns the VMS data, which may not necessarily be shared with others. ³⁹

2.2.2. Automatic Identification Systems (AIS)

Since 2004, the IMO requires AIS transponders to be installed on board all vessels of 300 gross tonnage and above engaged on international voyages, and all passenger ships irrespective of size. ⁴⁰ AIS enable the automatic exchange of navigational information between vessels and shore stations. AIS data are continuously transmitted by vessels, thus enabling their real-time tracking identification. ⁴¹ The transmissions are received without permission.

AIS is therefore the largest and most significant source of geospatial ship movement data. However, since vessel tracking is not its core purpose, it is complex to analyse the relevant data. In this respect, the use of artificial intelligence (AI) models is attaining increasing prominence, since AIS is the only dataset to which one can apply strong AI models because it is continuously transmitted in real time.

However, AIS has its inherent limitations: first, it is not mandatory for small vessels that fall outside the requirements of the International Convention for the Safety of Life at Sea. ⁴² Second, the range for ship-to-ship communications is usually 20 miles and, for ship to shore communications, only 40 miles. ⁴³ Third, and more importantly, the main deficiency of AIS, and VMS alike, is that they are cooperative in nature. This means that neither VMS nor AIS can track vessels which do not possess, or do not operate in a reliable fashion, the necessary transponders. ⁴⁴ Further, they can be turned off or electronically subverted, thus rendering the vessel concerned ‘dark’. ⁴⁵

2.2.3. Satellite surveillance technologies

In light of the deficiencies associated with the cooperative MDA tools, ‘non-cooperative’ tools involving earth observation tools through remote sensing satellites are increasingly used for vessel detection in vast areas. ⁴⁶ The key operational difference between these two models is reported by an expert as follows:

AIS-based monitoring is dynamic, especially if you can apply AI models to it. Remote-sensing capabilities on the other hand can only provide static monitoring—it is very difficult to understand or have evidence of vessel behaviours (except for transshipment) based on remote-sensing data only with currently available technologies. ⁴⁷

Satellite observations have the advantage that they can observe vast ocean areas repeatedly. However, all satellite sensors have specific limits on the size of the area that they can monitor. ⁴⁸

The most common sensor that is used for vessel detection is a Synthetic Aperture Radar (SAR) system which, by transmitting microwave radiation, enables measurements to be made in all weather conditions, a significant advantage for most marine environments. In fact, SAR technology has been used since February 2004 in the French Antarctic territories to tackle illegal fishing for Patagonian toothfish. ⁴⁹

The advantage of remote sensing tools is that they can cover large areas, they are not impeded by cloud cover or darkness, and they are much cheaper to acquire. ⁵⁰ However, since SAR images contain a huge amount of information, the need for processing by automatic detection software or algorithms becomes imperative. However, there should be sufficient human resources with the expertise to interpret such data. ⁵¹ Although AI cannot completely substitute human operators, automated technologies can provide substantial support in analysing data collected from the maritime domain, thereby enabling the examination of vast quantities of surveillance footage ⁵² in a cost-effective manner that is affordable to most States. ⁵³

2.2.4. Mind the gap: earth observation tools in high seas MPAs

Despite the unquestionable utility of earth observation tools for the surveillance of large maritime areas, to date there has been no satellite-based surveillance system operational over high seas MPAs. On the contrary, earth observation tools have been limited to use over MPAs or closed fishing areas within national jurisdiction. Notably, coastal States have increasingly resorted to private operators, like Skylight, ⁵⁴ Ocean Mind ⁵⁵ or Global Fishing Watch, ⁵⁶ to provide the requisite analytical tools. It remains to be seen whether and to what extent such tools will be used in high seas MPAs designated under the BBNJ Agreement. Their utility is self-evident in such remote and potentially vast maritime areas.

3. Surveillance in high seas MPAs as an assertion of flag State jurisdiction

Since the MPAs under consideration are located on the high seas, it is apparent that the implementation of MPAs and their related measures rests exclusively with flag States and, in particular, those flag States that are parties to the relevant instrument pursuant to which the MPA is established, be it—in the future—the BBNJ Agreement or another global or regional instrument. These States are under the obligation to ensure that their vessels are not acting in violation of the MPA and their related measures. ⁵⁷

Third States, i.e. States not party to such an instrument, for example the BBNJ Agreement, are not bound per se by the MPA related measures (pacta tertiis principle). ⁵⁸ It could be argued that the duty to respect those measures flows from such a protected area generating erga omnes effects as an ‘objective regime’. ⁵⁹ Nevertheless, in view of the controversial nature of the ‘objective regime’ theory, ⁶⁰ and the fact that high seas MPAs lack the territorial element with which such regimes are usually attached, ⁶¹ this argument is difficult to sustain.

As stated in Section 2.2.4, current high seas MPAs lack a detailed surveillance scheme providing for the use of earth observation tools. The BBNJ Agreement is also silent in this regard. Hopefully, in the future MPA management measures will include a detailed surveillance and enforcement mechanism, providing inter alia for the use of MDA tools. ⁶² Until then, and even in the absence of such mechanisms, this article argues that States are not only permitted but also obligated to conduct surveillance by all available MDA tools in relation to the activities of their vessels in high seas MPAs.

3.1. Permissibility of surveillance

On the high seas the predominant rule is freedom of navigation, which finds its expression in the exclusive jurisdiction of flag States over vessels flying their flag, enshrined in Article 92(1) UNCLOS. ⁶³ Flag State jurisdiction, which includes the jurisdiction to enact laws (legislative or prescriptive jurisdiction) and enforce them (enforcement jurisdiction), ⁶⁴ is exercised by the State whose flag the vessel in question is entitled to fly which, under the law of the sea, is the State of its nationality. ⁶⁵ Flag State jurisdiction is thus the capacity of the State of nationality of a vessel to assert prescriptive and enforcement jurisdiction over that vessel under international law. ⁶⁶

Since such jurisdiction is plenary in nature, it includes by necessary implication the capacity of the flag State to monitor its vessels’ activities as well as to take any necessary measures to ensure compliance with a high seas MPA. MCS measures fall clearly within the ambit of flag State jurisdiction, in particular its jurisdiction to enforce the MPA measures to which it has subscribed by being party to the relevant global or regional instrument or organisation. Hence, by virtue of their jurisdictional powers that they enjoy over their vessels on the high seas, flag States are entitled to monitor their activities in an MPA, including by resort to available earth observation tools.

3.2. Obligation of surveillance

Notably, the assertion of jurisdiction by the flag State under the law of the sea is in principle permissive, not mandatory. The assertion of jurisdiction is rendered compulsory only when the flag States concerned have assumed a relevant international obligation which requires them to exercise their prescriptive or enforcement jurisdiction. Thus, unless the flag States concerned have not assumed an obligation to this effect, it is within their discretion to conduct MCS over their vessels in a high seas MPA. This article contends that States are under such an obligation not only pursuant to specific regimes where applicable but, most importantly, under both UNCLOS and customary international law.

Briefly, by virtue of Part XII UNCLOS and customary international law, States are under certain specific obligations, including ‘to protect and preserve the marine environment’, ⁶⁷ to take ‘all measures consistent with this Convention that are necessary to prevent, reduce and control pollution of the marine environment from any source, using for this purpose the best practicable means at their disposal’, ⁶⁸ including those ‘necessary to protect and preserve rare or fragile ecosystems as well as the habitat of depleted, threatened or endangered species and other forms of marine life’. ⁶⁹

As the International Tribunal for the Law of the Sea (ITLOS) has opined, all these obligations are obligations of conduct, ⁷⁰ and thus of ‘due diligence’. ⁷¹ The crucial question of course is ‘what is the diligence that is due’? ⁷² In replying to this question in relation to climate change, ITLOS stated that:

the obligation of due diligence requires a State to put in place a national system, including legislation, administrative procedures and an enforcement mechanism necessary to regulate the activities in question, and to exercise adequate vigilance to make such a system function efficiently, with a view to achieving the intended objective. ⁷³

The pronouncement of the International Court of Justice (ICJ) in Pulp Mills on the River Uruguay, which described an obligation to act with due diligence, is also pertinent:

It is an obligation which entails not only the adoption of appropriate rules and measures, but also a certain level of vigilance in their enforcement and the exercise of administrative control applicable to public and private operators, such as the monitoring of activities undertaken by such operators. ⁷⁴

Consistent with the identification by the Seabed Disputes Chamber of ITLOS that ‘[t]he standard of due diligence has to be more severe for the riskier activities’, it is submitted that the standard of due diligence with respect to MPAs in vulnerable marine ecosystems should be ‘stringent’, given the high risks of serious and irreversible harm to the marine environment. ⁷⁵

In light of this, there is room to argue that in order to meet this stringent standard of due diligence in implementing MPAs and related measures, and thus ‘protecting and preserving rare or fragile ecosystems’ under Article 194(5) UNCLOS, States should necessarily be guided by the ‘best available techniques’ and ‘best practicable means’, which include earth observation tools, including remote sensing. Such tools fall neatly into the scope of ‘best available techniques’ for the surveillance of MPAs on the high seas and their effective implementation, as dictated by the ‘due diligence’ obligations under Part XII, mainly Article 194 UNCLOS. ⁷⁶ Hence, the use of such tools is instrumental in the discharge of all aspects of ‘due diligence’ duties by the flag State, namely: the introduction of policies, legislation and administrative controls; the exercise of vigilance and administrative controls in their implementation; and the employment of the ‘best available techniques’ to this end.

Thus, it is submitted that flag States are not only entitled but also obligated under UNCLOS to monitor their vessels on the high seas, including by all available tools, in accordance of course with their capabilities. ⁷⁷ Importantly, the due diligence to be displayed by flag States in this regard would be even more rigid in high seas MPAs pursuant to Article 194(5) UNCLOS. Significantly, also, such monitoring obligations exist regardless of any pertinent obligation under the relevant MPA instrument, for example under future BBNJ Agreement MPA-related measures, which would be applicable to BBNJ Agreement States Parties, since the legal basis rests with Part XII UNCLOS, as explained in Section 1. It is argued that such due diligence obligations also form part of customary international law. ⁷⁸

4. Surveillance and related actions in respect of foreign-flagged vessels in high seas MPAs

The next question concerns third States’ vessels. Are third States entitled to conduct any monitoring or surveillance over foreign flagged vessels in a high seas MPA? And what should they do if they spot any illicit activity from such vessels therein?

First, it is true that UNCLOS falls short of expressly providing for any right of States to request information from foreign-flagged vessels on the high seas or to monitor their activities. In the absence of such a permissive rule, it is questioned whether, on the contrary, international law contains any prohibition to this effect. As a corollary to the principle of the freedom of the high seas, all States enjoy the freedom of navigation on the high seas. ⁷⁹ Such freedom, as ITLOS acknowledged in the M/V “Norstar” case, ‘would be illusory if a ship—a principal means for the exercise of the freedom of navigation—could be subject to the jurisdiction of other States on the high seas’. ⁸⁰

In light of this, the pivotal question is whether the request for information from a foreign-flagged vessel on the high seas or, for the purposes of this article, the surveillance activities over such a vessel, amount to an interference with the freedom of navigation exercised by that vessel. If they do not, the surveillance activities would be in accordance with the law of the sea. ⁸¹ According to ITLOS:

any act of interference with navigation of foreign ships or any exercise of jurisdiction over such ships on the high seas constitutes a breach of the freedom of navigation, unless justified by the Convention or other international treaties. It goes without saying that physical or material interference with navigation of foreign ships on the high seas violates the freedom of navigation. ⁸²

It follows that, in order not to violate the freedom of navigation and thus be permissible, the act in question, i.e. the surveillance of foreign vessels, should neither result in an interference with the navigation of the vessel, nor should it subject the vessel and its activities to the jurisdiction of the State concerned, unless such interference would be otherwise justified under international law. Provided that surveillance measures, including those conducted by earth observation tools, are not followed by any enforcement measures, it is submitted that they do not amount to an interference with the freedom of navigation, as construed by ITLOS in M/V “Norstar”.

This assertion also finds support in State practice, legal doctrine and treaty law. ⁸³ Indeed, ‘it is a universally recognized customary rule of international law that warships of all nations, in order to maintain the safety of the high seas, have the power to require suspicious private vessels on the high seas to show their flag’. ⁸⁴ The right to approach, or reconnaissance, is limited to the right to approach a ship to identify it, including by requesting it to ‘show her colours’, which is prima facie evidence of its nationality, ⁸⁵ which today can be effected by modern technological means (e.g. AIS, Long-Range Identification and Tracking (LRIT)). ⁸⁶ Thus, it is argued that the mere monitoring or surveillance of vessels on the high seas is well within the bounds of international law as a measure of general policing of the oceans.

Next, the question arises as to what subsequent measures should be taken regarding the vessel acting in violation of the MPA. As noted, absent the consent of the flag State there is no room for any enforcement against these vessels on the high seas. First, it is submitted that, albeit not mandatory on the face of UNCLOS, States shall report to the flag State concerned any violation of the MPAs and related measures. It is true that Article 94(6) UNCLOS stipulates that ‘a State which has clear grounds to believe that proper jurisdiction and control with respect to a ship have not been exercised may report the facts to the flag State’. ⁸⁷ The term ‘may’ denotes a discretion on the part of the third State when it comes to such reporting and ‘it thus appears to provide, in formal terms, a relatively weak system of oversight’. ⁸⁸

However, if one reads Article 94(6) UNCLOS in its context, in particular Part XII, in light of the object and purpose of the Convention, ⁸⁹ which includes the protection of the marine environment, ⁹⁰ and in line with the principle of effectiveness or effet utile in treaty interpretation (ut res magis valeat quam pereat), ⁹¹ there is room to argue that States are indeed under a duty to report any violations taking place in MPAs. Such a duty would be consistent with the general obligation of cooperation under Article 197 UNCLOS, ⁹² which is further elaborated upon in Articles 198, 199, 200 and 201. ⁹³ Of particular relevance here is the duty of States to notify other States concerning imminent or actual damage to the marine environment. ⁹⁴ As ITLOS opined in relation to climate change:

In the Tribunal’s view, the duty to cooperate is reflected in and permeates the entirety of Part XII of the Convention. This duty is given concrete form in a wide range of specific obligations of States Parties, which are central to countering marine pollution from anthropogenic GHG emissions at the global level. ⁹⁵

In view of the urgent need to protect rare and fragile marine ecosystems, like those protected by high seas MPAs, it is submitted that whenever States become aware through MDA, including earth observation tools, of suspicious activities like dumping, illegal fishing or other illicit activities within an MPA, they are under the duty to notify, first, the flag State of the suspected vessel and, where appropriate, the competent international body (e.g. OSPAR, IMO, RFMOs etc).

Moreover, the duty to cooperate, as posited in UNCLOS and under customary international law, ⁹⁶ denotes, in the view of the author, a duty to share information with the flag State concerned in case of a relevant request. Such information may, arguably, include satellite data that private operators within the respective States’ jurisdiction, such as Skylight or Global Fishing Watch, may hold. However, as the Arbitral Tribunal in The Enrica Lexie Incident stated, a duty to cooperate is ‘a duty of a continuing nature – an obligation of conduct rather than a one-time commitment or result’. ⁹⁷ This means that while States are not obliged on each and every occasion to share information, including satellite data, they should nevertheless respond to any relevant request and, if they opt to deny the latter, justify this denial, for example on grounds of public security. ⁹⁸ This would also be in accordance with the principle of good faith enshrined in Article 300 UNCLOS. ⁹⁹

Noticeably, States would be under similar duties of cooperation, including sharing information on suspect vessels’ activities in high seas MPAs, by virtue of global and regional instruments, in particular related to fisheries. Suffice it to note Article 20(4) Fish Stocks Agreement provides that ‘States shall assist each other in identifying vessels reported to have engaged in activities undermining the effectiveness of subregional, regional or global conservation and management measures’. ¹⁰⁰ Also, under paragraph 2 of the same Article:

[a] flag State conducting an investigation of an alleged violation of conservation and management measures for straddling fish stocks or highly migratory fish stocks may request the assistance of any other State whose cooperation may be useful in the conduct of that investigation. All States shall endeavour to meet reasonable requests made by a flag State in connection with such investigations. ¹⁰¹

It follows that if a State Party to the Fish Stocks Agreement becomes aware of illegal fishing activity using earth observation tools within an MPA, that State is obligated to notify the other States Parties, including the flag State, of this activity. Further, States Parties are required to provide such evidentiary material, including satellite images, to requesting parties, e.g. flag States.

Similar cooperation requirements, as well as various enforcement actions, are also prescribed by RFMOs, including in relation to high seas MPAs. For example, with respect to the Ross Sea MPA established by CCAMLR in 2016, ¹⁰² the relevant Conservation Measure sets forth that the ‘Members participating in the CCAMLR System of Inspection are encouraged to carry out surveillance and inspection activities within the MPA to verify compliance with this conservation measure and other applicable conservation measures’. ¹⁰³ Also, more rigorous notification rules exist in relation to data obtained during inspections under RFMOs’ schemes. ¹⁰⁴

5. The use of satellite data for enforcement of high seas MPAs

Having mapped out the rights and obligations of States concerning surveillance of high seas MPAs, including through the use of earth observation tools, this article next examines how these tools may be conducive to the exercise of enforcement jurisdiction in this regard. According to Article 73 UNCLOS, enforcement jurisdiction denotes ‘such measures, including boarding, inspection, arrest and judicial proceedings, as may be necessary to ensure compliance with the laws and regulations adopted [by the coastal] State in conformity with this Convention’. ¹⁰⁵ Thus, enforcement jurisdiction in this regard would include not only the employment of the said tools for the surveillance of vessels, but also further enforcement measures over the vessels and the persons involved in their operation (unity of the vessel), ¹⁰⁶ to punish any infringement of the MPA associated measures.

As noted in Section 3.1, in view of the principle of exclusive flag State jurisdiction on the high seas, no State can take any enforcement measures, apart from the abovementioned reporting requirements, in relation to the activities of foreign-flagged vessels on the high seas. Any enforcement measure shall be predicated upon the consent of the flag State either ad hoc or pursuant to an already existing agreement. ¹⁰⁷

Should the flag State, or any other State permitted under international law to exercise enforcement jurisdiction in this regard, ¹⁰⁸ decide to initiate proceedings against the vessel and the persons involved for the the infringement of the MPA-related measures (e.g. dumping, ship-to-ship transfer or fishing activity), earth observation tools may prove to be vital. Indeed, in order to corroborate the infringement under scrutiny, States may readily use evidence derived from, inter alia, satellite-based remote sensing technology. This MDA technology is of undisputed evidentiary value, since satellite evidence can provide information about locations that are too difficult to obtain directly. In fact, satellite evidence can often provide the only evidence that captures a particular event, ¹⁰⁹ especially in remote maritime areas. Notably, satellite imagery and related spatial information, such as aerial photographs, geographic information systems and global positioning system data, have been used on a national level in environmental disputes, toxic torts, petroleum refinery class actions, chemical plant class actions, Hurricane Katrina-related damage claims and many others claims. ¹¹⁰

Satellite data is normally used in an evidential context in several ways. First, it can be used by a government or policing body to check compliance with specific legislation. Second, archives of satellite images can provide historical evidence where the temporal dimension of what happened is important. ¹¹¹ Third, where satellites are used for regulatory monitoring, the images themselves are often not used as evidence in court but to provide advance notification to the authorities that something illegal might have taken place. The actual evidence of the illegal act is then ascertained from subsequent ground inspections, and the satellite data is merely used as an intelligence prompt. ¹¹²

Moreover, earth observation technology, including data acquired through satellites, has been used in international litigation as a means of evidence produced by the parties in support of their claims. ¹¹³ For example, satellite information as evidence has been presented inter alia before the ICJ, ¹¹⁴ ITLOS ¹¹⁵ and international arbitral tribunals. ¹¹⁶

Given the difficulties of successfully prosecuting environmental offences, especially in vast maritime areas where physical evidence is often unobtainable, earth observation tools are increasingly being incorporated into coastal State legislation as a way of not only detecting but also proving unlawful fishing activity, or more aptly, as a presumption of such activity. ¹¹⁷ For example, some coastal States in Africa have specifically incorporated remote detection techniques into their legislation, including electronic surveillance, satellite surveillance, videographic and photographic means, which constitute conclusive proof of the offence unless proven otherwise. ¹¹⁸ Also, a widely adopted approach is simply to acknowledge in legislation the evidentiary value of VMS data; for example, pursuant to section 176(1) of Kenya’s Fisheries Management and Development Act 2016, ‘[t]he readings of any mobile transceiver unit or other electronic location device integral to a [VMS] shall be admissible as evidence and may be used as prima facie evidence of the facts that they aver’. ¹¹⁹

Of relevance is that under some legislation, satellite data, amongst other relevant material, may be used to support statutory presumptions of an illegal activity at sea and as the sole evidence to prove such activity. The most striking example is clearly the legislation in the Pitcairn Islands, a United Kingdom overseas territory, which stipulates that remote tracking systems, including satellites and drones, may be used as evidence for fisheries prosecutions. As provided by the Pitcairn Marine Protected Area Ordinance 2016, for the purposes of any prosecution under the Ordinance or the applicable Marine Protection Regulations (updated in 2022), the means through which a fishing vessel may be found or observed:

include, but are not limited to: (a) remote satellite technology; (b) electronic monitoring by a Vessel Monitoring System (VMS); (c) an Automated Information System (AIS); (d) unmanned aerial, surface or underwater vehicle observations; (e) video, radar, acoustical and visual observations; (f) any other means that can reasonably be used to determine vessel activity historically or in real time. ¹²⁰

To conclude, digital evidence, including satellite evidence obtained through remote sensing, is significant for the purposes of high seas MPAs’ enforcement. Indeed, satellite evidence may be used in court at a later stage to punish infringement of the MPA and its related measures, either in combination with physical evidence found during vessel inspection or autonomously. In this regard, the admissibility of satellite evidence depends largely on the procedural rules of the specific adjudicating court. Nevertheless, the extent to which such evidence would suffice for effective suppression is another question, which depends heavily on the national legislation in place but, more importantly, also on the quality of the evidence, e.g. the satellite imagery. Indeed, the probative value of satellite evidence will largely depend on its reliability as well as on its relevance to the adjudicated case. ¹²¹

6. Concluding remarks

The establishment of an effective network of high seas MPAs around the globe is instrumental to alter the trajectory of the oceans from one of degradation to one of recovery. This goal, however, cannot be achieved without ensuring that the MPAs and their protective measures will be implemented by all the relevant stakeholders. Admittedly, effective MDA, including the use of earth observation tools, could prove an invaluable asset for the surveillance and enforcement of MPAs, particularly in ABNJ. Thus, it must be one of the first priorities when planning and establishing MPAs and their associated protective measures. MDA may also furnish the necessary evidence to support further enforcement action, including criminal proceedings. Satellite evidence is, indeed, increasingly used by States to prove illicit activities in remote areas and their value as evidence depends on their authenticity, credibility and reliability.

Relatedly, States are under various duties in respect of the surveillance and enforcement of MPAs. Obviously, the key instrument in respect of the duty of surveillance of high seas MPAs is the one governing the MPA concerned. In the absence of any special provision to this effect, however, this article has argued that under UNCLOS States are not only permitted, but also obligated, to monitor their vessels in high seas MPAs, including through earth observation tools, in order to ensure that they are not acting in violation of the associated protective measures. Second, States are permitted to monitor the activities of foreign-flagged vessels as long as they do not interfere with their freedom of navigation without the consent of the respective flag State. Third, States are under a general obligation to cooperate with the view to protecting the marine environment, in particular vulnerable ecosystems such as those covered by an MPA, which includes the duty to share information on illicit activities of vessels therein. Finally, there are various global and regional instruments that may impose even more stringent duties on the respective States Parties.