In this case, the Tribunal found that:
- It had jurisdiction to hear and respond to the Request for Advisory Opinion;
- UNCLOS is the applicable law in this proceeding, as well as other relevant rules of international law not incompatible with it;
- Anthropogenic GHG emissions fall within the UNCLOS definition of “pollution of the marine environment”;
- Obligations under Articles 192 and 194 of UNCLOS are due diligence obligations, which are stringent, objective and not solely discretionary;
- States Parties have specific obligations under Article 194(1) to take all measures necessary to prevent, reduce and control pollution of the marine environment in light of climate change and ocean acidification;
- States Parties have specific obligations under Article 194(2) pertaining to actions within their jurisdiction and control;
- States have specific obligations applicable to specific sources of pollution to adopt and enforce national laws and regulations;
- States Parties have specific obligations under Article 192 of to protect and preserve the marine environment from the effects of climate change.
Background and Context
The International Tribunal for the Law of the Sea (ITLOS) is the first of three international legal bodies to give an Advisory Opinion (AO) on questions of State obligations regarding climate change and anthropogenic greenhouse gas emissions under international law.[1] An AO, while not legally binding like a “traditional” court decision, carries significant legal weight and authority. This is because, in an AO, the Tribunal is interpreting and providing a legal clarification on questions of existing law.
This AO was requested by the Commission of Small Island States on Climate Change and International Law (COSIS), which was established in 2021 by Antigua and Barbuda and Tuvalu. Since then, membership in COSIS (which is open to any member of the Association of Small Island States – AOSIS, all of whom are historically low-GHG emitting, but highly vulnerable to climate change impacts) has gained seven additional member-states.[2]
On 12 December 2022, COSIS filed its Request for AO with ITLOS, asking the Tribunal to clarify and specify the obligations States Parties have under the UN Convention on the Law of the Sea (UNCLOS) to protect and preserve the marine environment from anthropogenic climate change. This is significant because of the crucial role the ocean plays in the climate system and the extensive impacts that GHG emissions and global warming have already had on the ocean, including acidification, sea level rise and increased severe storm activity.
Specifically, COSIS asked the Tribunal what the specific State obligations are to:
- prevent, reduce and control pollution of the marine environment in relation to the deleterious effects that result or are likely to result from climate change, including through ocean warming and sea level rise, and ocean acidification, which are caused by anthropogenic greenhouse gas emissions into the atmosphere?
- protect and preserve the marine environment in relation to climate change impacts, including ocean warming and sea level rise, and ocean acidification?
Procedurally, the main issues addressed in the written submissions[3] and oral testimony pertain to the Tribunal’s jurisdiction to provide an AO in this matter, the admissibility of UNCLOS as relevant law in this proceeding, along with its complementarity with the international climate change legal regime, including the Paris Agreement.
Substantively, questions addressed in the written submissions and oral testimony include whether anthropogenic GHG emissions constitute pollution under the UNCLOS definition thereof, the nature of States Parties’ due diligence obligations under Part XII of UNCLOS (which governs the protection and preservation of the marine environment), as well as the specific obligations under Articles 192 and 194 of UNCLOS and their requisite approaches (e.g. best available science, taking “all measures necessary”, etc.).
Key Outcomes
(1) The Tribunal has jurisdiction to give an Advisory Opinion in this matter
COSIS submitted that ITLOS, as the guardian of UNCLOS, has jurisdiction to render an AO in this matter. First, COSIS argues, the first requirement that an “international agreement related to the purposes of the Convention specifically provides for the submission to the Tribunal of a request for an AO” was satisfied by the official COSIS agreement’s contents and its stated mandate.
The second prerequisite that a request for AO must be transmitted to ITLOS by a body authorized under such an agreement is satisfied, COSIS argued, by its members’ unanimous decision to authorize such submission. COSIS further argued that it met the final prerequisite that the requested AO is given on a legal question by the fact that the questions submitted are inherently legal as they pertain to the legal obligations under UNCLOS.
The Tribunal, in its AO, unanimously found that under the relevant statutory requirements, the three prerequisites are met and the Request for AO was properly submitted, and advisory jurisdiction properly conferred on the Tribunal.[4]
Regarding the discretion to accept and respond to the Request for an AO, ITLOS has previously found that such a request should only be refused for “compelling reasons”. COSIS argued that there are no such compelling reasons here and – to the contrary – there are compelling reasons to answer the questions posed. Some States Parties argued that the AO requests the Tribunal to make new law or take on a legislative role rather than an interpretive one and that the questions posed are overly broad.
The Tribunal found unanimously that, contrary to some States’ position that a lack of consent by third States constitutes grounds for declining to give an AO, such lack of consent has no bearing on the Tribunals discretion, especially considering the large number of States parties who participated in the proceeding by submitting both written statements and oral testimony. The Tribunal also unanimously rejected arguments that the Request for AO contained overly broad or unclear questions, or pertained to guidance not in respect of the requesting parties’ own actions.
Instead, the Tribunal acknowledged the importance of the questions in the Request for AO in light of the dire consequences of climate change. It further found unanimously that the questions raised in the Request are clear and specific enough to enable an AO and deemed it appropriate to render an opinion here.[5]
(2) UNCLOS is the applicable law in this proceeding, as well as other relevant rules of international law not incompatible with it.
Given that this case deals with legal complexities that are driven by the scientific inter-connection between the climate system and the ocean, the relationship between the two legal regimes that govern these systems is an important issue that must be addressed.
COSIS, in its written and oral submissions, presented that the two legal regimes (UNCLOS and the international climate change legal regime, including the Paris Agreement) are complimentary and mutually supporting. UNCLOS is the applicable law governing the protection and preservation of the ocean and the marine environment, and it must be informed by the climate regime with respect to matters concerning climate change-related impacts on the ocean, so COSIS submitted.
The Tribunal unanimously found that, under the relevant statutory language, the Tribunal must apply UNCLOS and other rules of international law not incompatible with it. Pointing to the constitutional and framework nature of UNCLOS, the Tribunal found that, in order to clarify and inform the meaning of its provisions, coordination and harmonization between UNCLOS and external rules is important.
General international rules on treaty interpretation require that any relevant international law, together with the appropriate context thereof, be taken into account. Further, UNCLOS itself speaks to the need for consistency and mutual supportiveness between applicable rules. The Tribunal recalled that it is a generally accepted principle that multiple sets of rules and norms that address a single issue should be interpreted to being a single set of compatible obligations.
Specifically, the Tribunal found that the extensive treaty regime addressing various aspects of climate change, including the Paris Agreement, present relevant external rules in the present case.[6]
(3) The definition of “pollution of the marine environment” includes anthropogenic GHG emissions
Article 1(1)(4) of UNCLOS defines “pollution of the marine environment” as ‘the introduction by man, directly or indirectly, of substances or energy into the marine environment, including estuaries, which results or is likely to result in such deleterious effects as harm to living resources and marine life, hazards to human health, hindrance to marine activities, including fishing and other legitimate uses of the sea, impairment of quality of use of seawater and reduction of amenities.’
COSIS argued that the scientific consensus (as presented in IPCC Reports, e.g.) is that anthropogenic GHG emissions into the atmosphere have caused the world’s oceans to draw down over 90% of excess heat and over 25% of carbon out of the atmosphere, causing ocean acidification, sea level rise, and extreme weather events. The ‘deleterious effects’ therefrom include destruction of marine ecosystems and livelihoods, as well as devastating food and water supplies and presenting existential threats to entire island nations.
This proposition, which was supported by most other Party submissions, has significant legal implications because it would mean that UNCLOS, in the relevant provisions at issue here, governs the acts and omissions by States leading to anthropogenic GHG emissions.
The Tribunal addressed this question by first acknowledging that the terms “climate change”, “greenhouse gas emissions” and “ocean acidification” are not found anywhere within UNCLOS, but accepts the definitions given in relevant legal instruments and authoritative scientific works.
Because the specific obligations under UNCLOS, that are the subject matter of the Request for AO, relate to preventing, reducing and controlling pollution of the marine environment ‘in relation to’ the deleterious effects that result or are likely to result from climate change and ocean acidification, such terms must be explored within the definition of pollution found in UNCLOS Article 1(1)(4).
The Tribunal found that the three criteria within the definition – 1) there must be a substance or energy, 2) this must be introduced by humans, directly or indirectly, 3) such introduction must result or be likely to result in deleterious effects – are cumulative and must all be met.
The Tribunal unanimously concluded, after an extensive discussion of the scientific processes involved, that anthropogenic GHG emissions into the atmosphere do indeed meet the criteria, and thus meet the definition of pollution of the marine environment under UNCLOS.[7]
Beyond this, the Tribunal found that obligations under UNCLOS to prevent, reduce and control marine pollution by anthropogenic GHG emissions apply to any source of such pollution, including sources on land, vessels, and by and through the atmosphere.
(4) Due Diligence obligations are stringent, objective and not solely discretionary
Beyond procedural questions before the Tribunal, a key question to be answered in the AO concerns the scope and specificity of the due diligence required of States under Part XII of UNCLOS, in the face of the high probability of disastrous harm to the marine environment from anthropogenic GHG emissions and climate change.
COSIS, in its submissions, points to the Tribunal’s prior jurisprudence on Part XII, which has confirmed that due diligence provides the standard of conduct in this context. There is broad agreement among other Party submissions that due diligence is a variable and contextual standard and that the required conduct by States to protect and preserve the marine environment is determined by several factors, including the degree of risk and the foreseeability and severity of the potential harm.
COSIS highlighted the Tribunal’s previous findings that States must “deploy adequate means, to exercise best possible efforts, to do the utmost”[8] to protect and preserve the marine environment, and that vigilance and prevention are required due to the irreversible nature of climate change-related damage to the marine environment.
Contrary to several Party submissions, COSIS contends that while due diligence obligations are contextual, States do not have boundless discretion in complying with their obligations. Rather, due diligence must be appropriate and proportional to the degree of risk involved.
The Tribunal found unanimously that obligations under Articles 194 and 192 are of a due diligence nature. The standard of due diligence required is stringent given the high risk of serious and irreversible harm to the marine environment from anthropogenic GHG emissions, the effects of climate change and ocean acidification.
The standard may be even more stringent when it comes to the obligation to prevent activities within a State’s jurisdiction and control from causing pollution to other States or the high seas due to the transboundary nature of the pollution caused by GHG emissions. However, the specific implementation of due diligence may vary based on a State’s capabilities and available resources.[9]
The Tribunal found that due diligence includes several important factors, including a degree of flexibility in order to accommodate the needs and interests of states with limited means and capabilities, indicating that those with greater means and capabilities must do more to reduce anthropogenic GHG emissions.
Due diligence, the Tribunal found, requires States 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.’[10]
(5) States Parties have specific obligations under Article 194(1) to take all measures necessary to prevent, reduce and control pollution of the marine environment in light of climate change and ocean acidification.
In its submissions, COSIS explored in detail the core obligations under Article 194 of UNCLOS that States shall take, individually or jointly, all measures necessary to prevent, reduce and control pollution of the marine environment in accordance with the best practical means at their disposal and in accordance with their capabilities.
COSIS submits that Article 194 presents a legal obligation, not a recommendation or suggestion, to take positive action to prevent, reduce and control pollution of the marine environment, and that the obligation requires States to take “all measures necessary” to satisfy this duty. COSIS submitted that the obligations under Article 194 are expanded and elaborated by further provisions under Part XII of UNCLOS, including those that govern pollution from sources on land, by vessels, and by and through the atmosphere. COSIS further submitted that the ‘best available science’ must be used to determine what is ‘necessary’ and points to the IPCC Reporting that limiting the average temperature increase to 1.5°C represents the current best available science and that, in order to comply with their obligations under Article 194, Parties must take action to at least limit global warming to 1.5°C.
The Tribunal outlined that the provisions in Part XII of UNCLOS govern the protection and preservation of the marine environment, imposing on States Parties various obligations, including the key provision in Article 194 requiring States to take all necessary measures to prevent, reduce and control pollution of the marine environment from “any source”. This obligation is complemented and elaborated on by further obligations under Part XII pertaining to specific sources of pollution and the obligations to adopt and enforce national legislation, and to establish and implement international rules and standards to regulate marine pollution.[11]
The Tribunal found unanimously that the specific obligation under Article 194(1) requires States to take all necessary measures to prevent, reduce and control marine pollution from anthropogenic GHG emissions and to endeavour to harmonize their policies in this connection. ‘All necessary measures’ includes those that are indispensable to prevent, reduce and control pollution, but also those that make achieving this goal possible, while not infringing other States’ rights.
The Tribunal agreed with many State’s submissions that what constitutes “necessary measures” should be determined objectively, and outlined several factors that States should consider in this assessment, including the best available science (found in IPCC reports) and international rules and standards, particularly the Paris Agreement’s 1.5°C temperature goal and the relevant timelines for the necessary emissions reduction pathways to achieve that goal. Other factors may include available capabilities and resources of the State. [12]
(6) States Parties have specific obligations under Article 194(2) pertaining to actions within their jurisdiction and control.
The Tribunal separately addressed obligations under Article 194(2) in relation to anthropogenic GHG emissions, which imposes the specific obligation to take all necessary measures to ensure that activities under their jurisdiction or control do not cause pollution to other States, and that any pollution that arises under their jurisdiction or control does not spread beyond their sovereign reach.
Crucially, the Tribunal found that “activities under their jurisdiction or control” is a broad phrase, including activities by both public and private actors and encompassing all areas in which a State exercises authority (such as on board ships or airplanes e.g.). Given the transboundary nature of GHG emissions and climate change, the obligation to prevent harm or pollution beyond a State’s borders under Article 194(2) imposes a more stringent due diligence obligation than the already stringent obligation under Article 194(1).
(7) States have specific obligations applicable to specific sources of pollution to adopt and enforce national laws and regulations[13]
The Tribunal, in answering Question a) regarding the specific obligations to prevent, reduce and control marine pollution caused by ‘anthropogenic GHG emissions into the atmosphere’, considered the most relevant sources of such pollution being from land-based sources, vessels and aircraft, each of which are addressed by provisions under Part XII of UNCLOS which complement and expand the general obligations set out in Article 194 (discussed above).
First, the Tribunal found unanimously that, regarding pollution from land-based sources and from or through the atmosphere, States have the specific obligations to adopt national legislation to prevent, reduce and control marine pollution from those sources, taking into account internationally agreed rules and standards. In the case of anthropogenic GHG emissions, the applicable international rules and standards are the international climate change legal regime and the Paris Agreement in particular, and other legal regimes governing ships and air pollution.
The Tribunal further unanimously agreed that States have the specific obligations to enforce such national laws and regulations, and to take measures necessary to implement the relevant and applicable international rules and standards to prevent, reduce and control pollution of the marine environment from these sources, which were established through competent international organizations or conferences.
When it comes to pollution from vessels under a State’s control, the specific obligations are to adopt laws and regulations that must at least have the same effect as the relevant generally accepted international rules and standards to prevent, reduce and control pollution of the marine environment. States further have the specific obligation to ensure compliance by their vessels with their laws to prevent, reduce and control pollution and also with relevant international rules and standards.
The Tribunal found further specific obligations to cooperate continuously, meaningfully and in good faith, in order to prevent, reduce and control marine pollution from anthropogenic GHGs; based on best available science, to cooperate in formulating and elaborating international rules, standards and recommended practices and procedures to counter marine pollution; cooperate to promote studies, scientific research and knowledge exchange, and to establishing scientific criteria as a basis for rules, standards and practices regarding marine pollution from anthropogenic GHG emissions.
The Tribunal also outlined specific obligations regarding assistance particularly to vulnerable developing States; monitoring and publishing reports of environmental impact assessments and continuing surveillance of impacts from activities which they have permitted which are likely to pollute the marine environment. States must also conduct environmental impact assessments of any planned activity – whether public or private – that may cause substantial pollution or significant harm, including cumulative effects.[14]
(8) States Parties have specific obligations under Article 192 to protect and preserve the marine environment from the effects of climate change.
COSIS submitted that the specific obligations under Article 192 to protect and preserve the marine environment from the effects of climate change include forward-looking obligations. To “protect” the marine environment, the obligation includes taking necessary measures to enable to continue to serve as a carbon sink, drawing down excess carbon emissions out of the atmosphere. This includes, so COSIS argued, reducing anthropogenic GHG emissions in line with best available science and international standards and undertaking comprehensive impact assessments, preserving and restoring degraded ecosystems and species that are instrumental in sequestering carbon.
COSIS further argued that the obligations under Article 192 include those measures necessary to adapt to adverse effects of climate change, taking nature-based and ecosystem-based approaches to protecting and restoring important and threatened marine ecosystems.
COSIS further argued that the obligations flowing from Article 192 require States to take national measures, such as adopting laws and regulations and ensuring implementation and enforcement thereof.
The Tribunal drew attention to the broad scope of Article 192, which simply provides that “States have the obligation to protect and preserve the marine environment,”[15] and once again found that the specific obligations this entails are further elaborated in Part XII of UNCLOS.
Agreeing with the majority of Party submissions, the Tribunal found that the obligation in Article 192 is broad and encompasses any type of harm or threat to, or degradation of, the marine environment, including climate change impacts like ocean warming, sea level rise and ocean acidification. Given that the ocean is the world’s largest carbon sink, the obligation to protect and preserve the marine environment has dual significance in both promoting the conservation and resilience of marine ecosystems and living resources, and also through measures to restore any degraded marine environment, thereby mitigating further anthropogenic GHG emissions.
Crucially, the Tribunal again pointed to the international climate change legal regime, including the Paris Agreement, and other relevant international rules as not only being compatible with the obligations under Article 192, but also exemplifying how science and other international rules are taken into account in complying with these obligations.
Ultimately, the Tribunal found unanimously that Article 192 imposes a general obligation on States Parties to protect and preserve the marine environment from climate change impacts, such as ocean acidification, ocean warming and sea level rise.[16]
Climate change litigation implications
The AO from ITLOS is the first of three international legal opinions on the question of state obligations as it pertains to anthropogenic greenhouse gas emissions and the impacts of climate change under international law. While Advisory Opinions are not binding law in the way that court decisions on legal disputes are, they do carry significant legal weight in that, rather than making law, they interpret, clarify and define State obligations under existing law.
There are several broad implications of this AO for climate change related litigation.
First, the Tribunal’s extensive descriptions of the specific obligations regarding specific sources of pollution include obligations to enact and enforce national laws and regulations to prevent, reduce and control pollution of the marine environment from anthropogenic GHG emissions. In the context of climate change litigation in national court settings, these specific requirements could very well strengthen legal arguments when a State’s national climate policy is being challenged as being insufficient to meet the Paris Agreement’s temperature goals.
Just as international climate change law (the Paris Agreement, e.g.) is relied on in such cases to demonstrate a State’s insufficient actions, a State’s specific obligations under UNCLOS to enact and enforce adequate laws and regulations to prevent the pollution of the marine environment from anthropogenic GHG emissions could be used. The Tribunal’s findings certainly care out further potential substance to be argued within the obligations of States under the Paris Agreement to exercise due diligence in order to reduce their emissions to the highest possible extent.
Further, the Tribunal’s finding that the determination of what constitutes “necessary measures” is an objective one, based on best available science and internationally agreed rules and standards has potential implications. This could both weaken arguments based on the broad discretion afforded to States (based in part on the concept of separation of powers) and could strengthen arguments in favour of reducing such broad State discretion.
Second, the Tribunal’s findings regarding Article 194(2) of UNCLOS could have implications for climate change-related litigation. Specifically, the requirement that States take all measures necessary to ensure that activities under their “jurisdiction or control” do not cause damage by pollution, as well as potential responsibility for any pollution arising from incidents or activities (again “under their jurisdiction or control”). The Tribunal was clear that this extends to both public and private actors. This means that States must also act appropriately to ensure that the activities of any private entities within their jurisdiction or control, that cause anthropogenic GHG emissions, are effectively regulated. The finding adds pressure on States to strengthen scrutiny on the activities of major carbon emitters in the country, as they could face UNCLOS-based legal challenges from civil society for lax regulatory standards or deficient oversight and enforcement.
Third, as mentioned above, this is the first of three expected Advisory Opinions from international legal bodies. While the other courts are not bound to follow this AO, they will certainly give deference and weight to the Tribunal’s findings, and this may impact their own findings. The Tribunal’s extensive and detailed review of the implications of climate change under international law (of the sea) is likely to encourage equivalent consideration on the merits of the questions related to climate-related obligations under other sources of international law.
[1] The International Court of Justice (ICJ) and the Inter-American Commission on Human Rights (IACHR) have both also received official Requests for AOs regarding climate change-related State obligations.
[2] COSIS membership now includes: Antigua and Barbuda, Tuvalu, Palau, Niue, Vanuatu, St. Lucia, St. Vincent and the Grenadines, St. Kitts and Nevis
[3] 34 States and 19 intergovernmental organisations and other groups submitted written statements.
[4] Case No. 31 Advisory Opinion, paras 84 – 109
[5] Case No. 31 AO, paras 110 – 122
[6] Case No. 31 AO, paras 123 – 137.
[7] Case No. 31 AO, paras 159 – 179, 189.
[8] Responsibilities and obligations of States with respect to activities in the Area, Advisory Opinion, ITLOS Reports 2011, para 110.
[9] Case No. 31 AO, paras 223 – 242, 254 – 257, 395 – 400.
[10] Case No. 31 AO, para 235.
[11] Case No. 31 AO, paras 180 – 192.
[12] Case No. 31 AO, paras 193 – 243.
[13] Case No. 31, paras 259 – 291.
[14] Case No. 31 AO, paras 292 – 367.
[15] UNCLOS, Article 192.
[16] Case No. 31 AO, paras 369-400.