The Most Extensive Case Before the International Court of Justice: Obligations of States in respect of Climate Change
The impact of human society on climate change represents one of the most pressing challenges of our time, requiring collective action at the global level to avert catastrophic consequences for the environment and humanity as a whole. According to the World Meteorological Organization, 2024 was the first year in which the global average temperature exceeded 1.5°C above pre-industrial levels. The scientific consensus points to the urgent need for immediate and systemic intervention, yet the response of the majority of the international community remains insufficient. Small island developing States face the threat of complete disappearance due to sea-level rise, making it unsurprising that the initiative to bring proceedings before the International Court of Justice (ICJ) originated from Vanuatu, a country that faces a great risk because of its geographic characteristics and exposure to extreme weather conditions. In this context, international law emerges as a mechanism capable of articulating States’ legal obligations and contributing to greater legal certainty with respect to States’ duties regarding human impacts on the environment. It is becoming increasingly clear that political agreements are insufficient, and that reliance on legal mechanisms is necessary to define, articulate, and enforce such obligations.
This text first sets out the background of the initiative and the legal basis for the proceedings, highlighting their significance, then presents the main arguments advanced by relevant stakeholders, and concludes with comparative examples and a discussion of the potential implications of the ICJ’s Advisory Opinion for the future development of the international legal regimen on climate obligations.
Origin of the Initiative and Commencement of Proceedings Before the ICJ
In 2019, the organisation Pacific Island Students Fighting Climate Change was established by law students at the University of the South Pacific with the aim of persuading their national leaders to submit the question of States’ obligations regarding climate change and human rights to the ICJ. Their initiative succeeded in March 2023 when the Republic of Vanuatu, during a meeting of the United Nations General Assembly, proposed Resolution 77/276 with the support of 131 co-sponsoring States, including Serbia. The proposal relied on Article 65 of the Statute of the ICJ, which empowers the Court to render advisory opinions on legal questions at the request of certain UN organs. Article 96 of the UN Charter authorises the General Assembly and the Security Council to request an advisory opinion on any legal question.
By consensus and without a formal vote, the Resolution was adopted, submitting the following questions to the ICJ:
What are the obligations of States under international law to ensure the protection of the climate system and other parts of the environment from anthropogenic emissions of greenhouse gases—for States and for present and future generations?
What are the legal consequences under these obligations for States which, by their acts or omissions, have caused significant harm to the climate system and other parts of the environment, in relation to:
i. States, in particular small island developing States, which, due to their geographical circumstances and level of development, are injured or specially affected by or are particularly vulnerable to the adverse effects of climate change;
ii. peoples and individuals of the present and future generations affected by the adverse effects of climate change.
Legal and Political Significance of the Case
The historical importance of this proceeding is reflected in several aspects. Ninety-one written statements, 66 written comments, and oral submissions by 96 States and 11 international organisations make this the most extensive case in ICJ history by the number of submissions and participants. It is also the first time that the ICJ has considered the issue of climate change and State responsibility for addressing it, linking it to human rights and the concept of intergenerational equity, the obligation of current generations to manage natural resources and the environment in a way that allows future generations to meet their own needs. Although not yet codified in a binding international legal instrument, the ICJ implicitly recognised this concept in its 1996 Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, noting the need to take into account potential harm to future generations.
Introducing the perspective of future generations into legal analysis represents an innovation with the potential to transform how State responsibility is assessed in the context of climate change. ICJ advisory opinions are not legally binding, yet they carry great authority as interpretations of international law[1] and can influence judicial decisions, diplomatic processes, and the development of both national legislation and international legal norms. The fact that this initiative originated from students and small Pacific States underscores the role of civil society and the Global South in shaping international legal standards.
Illustrative Legal Interpretations
This section will present the main legal positions on the sources and scope of States’ obligations in the field of climate change, as set out by some of the participants in these proceedings in their written statements.
The Organization of the Petroleum Exporting Countries (OPEC) states that the international legal regime governing climate change is fully regulated by the existing treaties—the United Nations Framework Convention on Climate Change, the Kyoto Protocol, and the Paris Agreement—which together constitute a lex specialis, meaning a special legal regime under which these treaties take precedence over general legal norms. On this interpretation, States’ obligations cannot be expanded beyond provisions in those treaties; in other words, there is no legal basis to hold States responsible on the basis of general principles such as due diligence (the obligation of a State to take all reasonable measures to prevent any foreseeable harm) or the prevention of transboundary harm (the principle that no significant harm can be caused from one’s own territory to the territory of another State). In contrast, the Commission of Small Island States, of which Vanuatu—the initiator of these proceedings—is a member, insists that States’ obligations under international law with respect to climate change derive not only from the treaties mentioned above, but also from customary international law, human rights law, and the principle of intergenerational equity.
Kenya has emphasised that African States are disproportionately affected by climate change despite their minimal contribution to global emissions, and that climate obligations are intrinsically linked to the protection of human rights, including the rights to life, health, and access to food and water. Accordingly, Kenya maintains that the non-fulfilment of climate obligations which causes significant harm to States that have contributed the least to this crisis entails responsibility in the form of reparations, including financial compensation, since restitution is most often impossible in such situations.
The United States, on the other hand, takes the position that under existing treaties States are obligated only to make reasonable efforts, without responsibility for achieving specific results, and that this obligation does not entail sanctions in the event of insufficient emissions reductions. This view relies on the Paris Agreement (from which the US withdrew again in January 2025), which established Nationally Determined Contributions (NDCs) as measures that each State independently determines in pursuing global climate objectives, thereby creating a legal regime based on transparency and review rather than sanction.
These examples point to a general trend of deep division among the participants in the proceedings regarding the understanding of the sources and content of climate obligations. States most affected by the consequences of climate change advocate for a normative approach that entails a broader, materially binding framework. By contrast, actors with greater economic and political influence often favour a more restrictive interpretation of climate obligations, seeking to preserve greater discretion in shaping their policies.
Comparable Proceedings and Decisions
The proceedings brought by a Swiss organisation of women over the age of 64, concerned about the impact of extreme heatwaves on their health, have redefined the standards of State responsibility within the Council of Europe. In its judgment in Verein KlimaSeniorinnen Schweiz and Others v. Switzerland, the Grand Chamber of the European Court of Human Rights (ECtHR) found, for the first time, that a State’s failure to fulfil its climate-related obligations can amount to a violation of human rights, specifically Article 8 of the European Convention on Human Rights, which guarantees the right to respect for private and family life.
The Strasbourg Court derived from this provision positive obligations on States to establish, through their domestic regulatory frameworks, ambitious, time-bound targets for reducing greenhouse gas emissions, with the ambition to reach climate neutrality. Although no violation of Article 2 of the Convention, which protects the right to life, was found, the ECtHR recognised a strong similarity between the principles underlying these two provisions, particularly in the context of protection against foreseeable and irreversible environmental risks. Although this judgment was rendered in proceedings against Switzerland, the principle of legal certainty and the binding nature of the Court’s case law require that interpretations of the Convention, once established, are applied to all member States, including Serbia.
The growing trend of interest in climate change and States’ obligations in that regard has extended to other continents, including the Americas and Africa. The 2017 Advisory Opinion of the Inter-American Court of Human Rights marked a turning point in the recognition of the autonomous right to a healthy environment as a human right. On 3 July 2025, the Court delivered a new Advisory Opinion affirming the right to a stable climate as part of the corpus of human rights. It stated that the obligation of States to prevent irreversible harm to the environment and climate constitutes a jus cogensnorm, making it a fundamental, legally-binding rule of international law from which no derogation is allowed. A notable development is the Court’s recognition of the rights of nature as an independent legal subject, establishing corresponding State obligations to ensure its protection, restoration, and regeneration. Although these interpretations remain legally non-binding, their influence on the interpretation and development of national legislation is undeniable (for example, Costa Rica has incorporated climate justice issues into its National Decarbonisation Strategy, and a court in Peru has recognised the Marañón River as a legal subject).
A request has also been submitted to the African Court on Human and Peoples’ Rights for an advisory opinion concerning the interpretation of Article 24 of the African Charter on Human and Peoples’ Rights, which guarantees the right to a general satisfactory environment favourable to development, in the context of the climate crisis. A coalition comprising the Pan African Lawyers Union, the African Climate Platform, Natural Justice, and other civil society organisations is seeking clarification of States’ positive obligations regarding adaptation and mitigation in response to climate change. The request also raises questions of territorial jurisdiction in cases of transboundary harm, as well as State responsibility in relation to the activities of third parties, such as multinational corporations.
The Advisory Opinion of the International Tribunal for the Law of the Sea (ITLOS) offers another indication of the line of reasoning that the ICJ might adopt. In its legally non-binding advisory opinion, the Tribunal determined that anthropogenic greenhouse gas emissions constitute pollution of the marine environment within the meaning of Article 1 of the United Nations Convention on the Law of the Sea (UNCLOS). This finding explicitly links climate change, for the first time, to States’ legal obligations in the context of marine environmental protection. It was established that States Parties to UNCLOS have specific positive obligations to take all necessary measures to prevent, reduce, and control such pollution, including the establishment of national regulatory frameworks based on the best available scientific knowledge. Significantly, the Tribunal rejected the argument that the Paris Agreement fully regulates this area, emphasising that UNCLOS imposes additional, autonomous obligations.
Conclusion — Awaiting the Advisory Opinion
The ICJ is expected to deliver its advisory opinion in 2025. While not legally binding, the Court’s authoritative interpretation, given its institutional weight and the importance of the issues, will significantly influence the clarification of States’ current obligations and potentially lay the groundwork for future engagement of the international community in addressing climate change.
[1] ICJ in the case Legality of the Threat or Use of Nuclear Weapons (1996), par. 13
