On 21 May 2024, the International Tribunal for the Law of the Sea (ITLOS) delivered a highly anticipated (unanimous) Advisory Opinion on the Request submitted to ITLOS by the Commission of Small Island states on Climate Change and International Law.
ITLOS has clarified that States party to the United Nations Convention on the Law of the Sea (UNCLOS) have specific obligations to prevent, reduce and control pollution, including greenhouse gas (GHG) emissions, and their detrimental effects on the marine environment. Significantly, ITLOS opined that these obligations go beyond existing commitments to address and mitigate climate change impacts under the Paris Agreement.
This is the first time an international court or tribunal has addressed States’ obligations to combat climate change within the framework of the 1982 UNCLOS. This Advisory Opinion is the first of three advisory opinions on climate change expected to be issued by international and regional courts and tribunals in the coming year. Climate change-related opinions are expected from the Inter-American Court of Human Rights and the International Court of Justice, later in 2024 and 2025 respectively. All three advisory opinions will be pivotal in defining, and potentially expanding the existing scope, of the legal duties that States and corporations must address climate change.
We outline below the key findings of ITLOS in this most recent Advisory Opinion and the implications for States’ specific obligations to address climate change under UNCLOS. We also analyse how the Advisory Opinion may impact future climate litigation and the broader implications for private actors and companies.
Key takeaways:
ITLOS determined that States have an obligation to take all necessary measures to prevent, reduce and control marine pollution from GHG emissions under Article 194 of UNCLOS, considering the ‘best available science’ and relevant international rules and standards. In reaching this position, ITLOS made the unprecedented recognition that GHG emissions are a form of marine pollution.
While ITLOS was not invited to consider the legal consequences arising from a breach of these obligations, it did emphasise that if a State fails to comply with this obligation, ‘international responsibility would be engaged for that State’ and therefore failure to comply could give rise to a (increased) risk of litigation.
States must exercise due diligence to prevent, reduce and control marine pollution from GHG emissions and apply the precautionary approach (i.e. scientific uncertainty should not be used as a reason for postponing measures to prevent or minimise harm).
UNCLOS sets out specific obligations for States in respect of climate change, requiring States to go beyond their obligations under the Paris Agreement. While UNCLOS makes no explicit reference to the term ‘climate change’, relevant external rules concerning climate change, such as the Paris Agreement, are crucial for interpreting and contextualising the UNCLOS provisions.
ITLOS determined that contributing to the adverse impacts of the climate crisis on marine environments may amount to a violation of obligations under UNCLOS if not adequately mitigated.
While this (non-binding) Advisory Opinion considers States’ obligations, ITLOS’s findings are likely to have broader implications for companies in terms of growing regulatory, litigation and reputational risks. The Advisory Opinion is part of a growing body of international and domestic law on climate change action. Notably, the Advisory Opinion provides another avenue to pursue claims against states and corporations, unlocking the potential of UNCLOS as a climate protection instrument. The arguments put forward and the judicial comments in the Advisory Opinion may also form part of the increasing number of novel climate-related arguments being invoked to highlight the role businesses have in mitigating the climate crisis.
The International Tribunal on the Law of the Sea
ITLOS is an independent judicial body established by the 1982 United Nations Convention on the Law of the Sea (UNCLOS). UNCLOS is an international agreement that establishes rules governing all uses of the oceans and their resources, and all marine and maritime activities.
ITLOS has jurisdiction over any dispute concerning the interpretation or application of UNCLOS, and over all matters specifically provided for in any other agreement which confers jurisdiction on ITLOS. Disputes relating to UNCLOS may concern the conservation and management of the living resources of the sea, protection and preservation of the marine environment and marine scientific research.
Request for Advisory Opinion
On 12 December 2022, the Commission of Small Island States on Climate Change and International Law (Commission), comprising small island states including Tuvalu, Vanuatu and the Bahamas, requested ITLOS to give an Advisory Opinion on two specific questions:
“What are the specific obligations of State Parties to the UNCLOS, including under Part XII:
to prevent, reduce, and control pollution of the marine environment concerning the deleterious impacts stemming from climate change, such as ocean warming, sea level rise, and ocean acidification, caused by human-induced greenhouse gas emissions into the atmosphere?
to safeguard and conserve the marine environment regarding climate change repercussions, encompassing ocean warming, sea level rise, and ocean acidification?"
In its concluding oral submissions, the Commission asked ITLOS “to state, clearly and objectively what the current legal duties of States Parties are under UNCLOS in relation to the impact of climate change on the marine environment”.
Over 50 States, intergovernmental and non-governmental organizations, and other entities submitted written and oral arguments, reflecting diverse perspectives on how to address these questions.
ITLOS determined it was appropriate, and within its jurisdiction, to render the requested Advisory Opinion. ITLOS noted it is “conscious of the deleterious effects climate change has on the marine environment and the devastating consequences it has and will continue to have on small island States, considered to be among the most vulnerable to such impacts”.
ITLOS’s Findings
In summary, ITLOS clarified that States have specific obligations to take all necessary measures to prevent, reduce and control marine pollution from anthropogenic GHG emissions and to endeavour to harmonise their policies to be able to do this. These measures should be determined objectively, considering the best available science and relevant international rules and standards. This obligation is one of due diligence, which will be held to a high standard, given the high risks of serious and irreversible harm to the marine environment from GHG emissions.
In terms of international cooperation, ITLOS said that States had an obligation to prevent climate change-related pollution affecting other States and the environment beyond its national jurisdiction. States’ obligations further include joining in global efforts to address climate change and assist developing States, in particular vulnerable developing States.
ITLOS’s Opinion is particularly relevant for the implementation of the right to a clean, healthy and sustainable environment, recognised by the United Nations in July 2022. This is highlighted in the Amicus Brief jointly submitted by the Special Rapporteurs on Human Rights and Climate Change, Toxics and Human Rights, and Human Rights and the Environment, to assist ITLOS in its response to the Advisory Opinion Request. The Amicus Brief submitted that GHG emissions amount to pollution of the marine environment under UNCLOS, threatening a range of human rights, including the right to a clean, healthy and sustainable environment, which encompasses a safe climate, clean air, clean water and non-toxic environments.
ITLOS emphasised that the precautionary approach should be applied in the context of States’ obligations to conduct environmental and socio-economic assessments of any activity that may cause climate change-related marine pollution (i.e. scientific uncertainty should not be used as a reason for postponing measures to prevent or minimise harm).
ITLOS provided the following critical factual and legal determinations about the State’s obligations under UNCLOS.
ITLOS initially addressed the issue of whether GHG emissions fall within the definition of ‘pollution of the marine environment’. This determination was pivotal, as certain State obligations under UNCLOS are contingent upon whether anthropogenic GHG emissions constitute ‘pollution of the marine environment’.
ITLOS found GHG emissions satisfied the criteria of being a ‘substance or energy’ that is introduced into the marine environment ‘directly or indirectly’ by humans, resulting in various deleterious effects, as substantiated by scientific evidence and widely recognised by States. ITLOS therefore concluded the release of anthropogenic GHG emissions into the atmosphere constitutes pollution of the marine environment within the meaning of Article 1(1)(4) of UNCLOS.
In reaching this decision, ITLOS heavily relied on reports from the Intergovernmental Panel on Climate Change (IPCC), deemed authoritative assessments of climate change science and reflective of scientific consensus.
Article 194 of UNCLOS imposes two key obligations on States to take all necessary measures to (1) prevent, reduce and control marine pollution, and manage existing marine pollution, to prevent such pollution entirely; and (2) ensure certain situations relating to pollution do not occur.
Given ITLOS’s determination that GHG emissions in the atmosphere constitute pollution of the marine environment, it followed that Article 194(1) requires States to take all necessary measures to mitigate, manage and ultimately eliminate all GHG emissions that might directly or indirectly affect the marine environment, regardless of their origin.
In determining what ‘’all necessary measures’ means, ITLOS stated this should be understood broadly. Assessing what measures are 'necessary’ involves a fact-intensive analysis considering various objective factors, including the resources and capabilities available to States. ITLOS emphasised that in the context of marine pollution GHG emissions, States with greater means and capabilities must do more to reduce such emissions. States must have regard to both the best available science and a precautionary approach to regulating marine pollution from GHG emissions. ITLOS noted the precautionary approach is particularly important given the serious and irreversible damage that may be caused to the marine environment by GHG emissions pollution.
ITLOS came to the view, given the risks posed to the marine environment (including from climate change impacts and ocean acidification), States are required under UNCLOS to take measures as far-reaching and efficacious as possible to prevent or reduce the deleterious effects of climate change and ocean acidification on the marine environment.
ITLOS considered that the obligation under Article 194(1) contains some elements of the differentiated responsibilities and respective capabilities principle recognised in the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. When applied, this principle assigns differing obligations to States based on their needs, circumstances, future economic development, and historical contributions to climate change. Thus, the scope of the measures available to States may differ between developed and developing States. However, ITLOS confirmed all States must make mitigation efforts and endeavour to harmonise their policies to take necessary measures to prevent, reduce and control marine pollution.
ITLOS clarified Article 194(1) requires States to act with ‘due diligence’ in taking necessary measures to prevent, reduce and control marine pollution and that the standard of due diligence is ’stringent’. According to ITLOS, this due diligence obligation requires States to establish a national system comprising legislation, administrative procedures and an enforcement mechanism necessary for regulating relevant activities and to ‘exercise adequate vigilance’ to ensure the effective functioning of such a system. Significantly, ITLOS affirmed that if private entities or individuals conduct activities contributing to marine pollution, a State that has exercised due diligence should not be held accountable - it would be unreasonable, ITLOS stated, to hold a State, that has acted with due diligence, responsible for a private entity’s pollution.
Article 194(2) of UNCLOS requires States to take all measures necessary to ensure (a) activities under their jurisdiction or control do not cause damage by pollution to other States and their environment, and (b) pollution arising from incidents or activities under their jurisdiction or control does not spread beyond the areas where they exercise sovereign rights. ITLOS noted this obligation bears a close resemblance to the principle of harm prevention. In terms of specific sources of pollution, ITLOS noted marine pollution from anthropogenic GHG emissions can be characterised as pollution from land-based sources, pollution from vessels, or pollution from or through the atmosphere.
ITLOS affirmed this separate obligation under Article 194(2) of UNCLOS to prevent transboundary pollution was also triggered in the context of marine pollution by GHG emissions. While acknowledging that determining the causal link between anthropogenic GHG emissions from activities under one State's control and the damage elsewhere might be challenging, ITLOS asserted that States are still obliged to implement all necessary measures to ensure that such activities do not harm the environment elsewhere. According to ITLOS, this due diligence standard under Article 194(2) can be ‘even more stringent’ than that under Article 194(1), because of the nature of transboundary pollution.
ITLOS set out a range of specific obligations that are imposed on States by UNCLOS to adopt national legislation and mitigation practices, and to work together to establish international rules and standards. These are:
to adopt national legislation, take all other necessary measures, and endeavour to establish international rules, standards, and best practices and procedures to prevent, reduce and control pollution of the marine environment (Arts 207, 211 and 212);
to adopt and enforce national laws and regulations to prevent, reduce and control pollution of the marine environment from GHG emissions from land-based sources and from or through the atmosphere (Arts 213 and 222);
to cooperate, directly or through competent international organisations, continuously, meaningfully and in good faith to prevent, reduce and control marine pollution from GHG emissions (Arts 197, 200 and 201, read together with Arts 194 and 192);
developing a common regulatory framework for the protection and preservation of the marine environment (Art. 197); and
monitoring the risks and effects of pollution, publishing reports and undertaking environmental impact assessments (EIAs ) of activities. ITLOS emphasised that EIAs are crucial and must be undertaken for any planned activity, either public or private if there are “reasonable grounds for believing” that the activity could lead to substantial pollution to the marine environment or significant and harmful changes through GHG emissions (Arts 204 to 206).
ITLOS also addressed whether States' obligations under UNCLOS align with those of the Paris Agreement or necessitate additional measures beyond those contemplated by the Paris Agreement.
ITLOS concluded that a State’s obligations under UNCLOS go beyond existing commitments under the Paris Agreement. Relevantly, ITLOS opined that a State's obligation under Article 194 of UNCLOS cannot be considered fulfilled solely by complying with the obligations and commitments under the Paris Agreement. ITLOS noted that "the Paris Agreement does not compel Parties to reduce GHG emissions to any specific level within a mandatory timeline but allows each Party to determine its own national contributions”. Conversely, Article 194 imposes on States a "legal obligation to take all necessary measures to prevent, diminish, and manage marine pollution resulting from anthropogenic GHG emissions, including measures to reduce such emissions”. Failure to do so would incur international responsibility for the State.
ITLOS noted that while the term ‘climate change’ does not explicitly appear in UNCLOS, ‘relevant external rules’ concerning climate change, such as the Paris Agreement, are in place. According to ITLOS, these external rules are crucial for interpreting and contextualising UNCLOS provisions, with UNCLOS rules to be understood in a manner consistent with these external norms but without undermining UNCLOS' objectives.
Implications of ILTOS’ first Climate Change Advisory Opinion for States and Companies
This Advisory Opinion has valuably clarified the extent of States' international obligations regarding climate change under UNCLOS. With 169 State Parties to UNCLOS, this decision is likely to strengthen State actions regarding climate change and marine pollution going forward, as well as inform State’s approaches to EIA regulations. As noted above, this Advisory Opinion will likely influence the Inter-American Court of Human Rights and the International Court of Justice as they prepare to issue their own opinions on climate change.
The instances of States being held accountable for inadequate climate change action and being directed by Courts to take more ambitious action, whether generally or through the imposition of specific targets or measures, is increasing across all jurisdictions. According to the United Nations Environment Programme, climate litigation has more than doubled in the past five years. ITLOS’s clarification on States’ obligations in the context of climate change and international law will likely inform future climate change litigation in national and international courts and tribunals, including novel climate-related and marine pollution arguments.
ITLOS's Advisory Opinion may also have broader implications for private actors and companies. While the Advisory Opinion addresses the scope of States' international obligations, ITLOS made clear that where States have appropriate due diligence procedures in place, they should not be held responsible for pollution caused by private entities. This reinforces private entities must be cognisant of potential pollution of the marine environment because of GHG emissions, particularly where States impose obligations under domestic law to protect, mitigate or reduce harm to the marine environment.
As pressure on States to implement ambitious measures to address climate change continues to grow, private entities must be aware of the emerging trends in international law and the potential implications for domestic regulation and industry standards (such as disclosure standards).
While not yet in the specific circumstances of marine pollution, private entities are also being held accountable for insufficient climate action, including for not taking steps to reduce GHG emissions. Most notably (but by way of example only) this includes the landmark Dutch case Milieudefensie et al v Royal Dutch Shell plc , where Shell was ordered by a Dutch District Court to reduce its global carbon emissions by 45% by 2030 (Shell filed an appeal in July 2022 which was heard in April 2024). The ongoing case of Smith v Fonterra is another example, in which the Supreme Court of New Zealand most recently held that the applicant’s climate change tort claims of public nuisance, negligence and a novel climate duty, against New Zealand’s seven largest GHG emitters, was justiciable. These are only a handful of examples of what is an increasing body of case law.
It is therefore paramount for all states and entities to closely follow the evolving space of climate-related litigation and developing obligations under domestic and international law.
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