Students Win Historic Advisory Opinion from ICJ
On 23 July 2025 Judge Iwasawa Yuji, President of the International Court of Justice delivered the Court’s Advisory Opinion on the Obligations of States in respect of Climate Change.
This is a case of massive international importance which we will still be unpacking in the months and years to come. Our initial comments on the judgement consider these questions:
Who brought the case?
What were the questions at issue?
How was it argued and who participated?
What has the Court decided?
What effect will the judgement have?
Afterword about Vanuatu and Pacific Island Students Fighting Climate Change
Who brought the case?
The case was formally referred to the Court by 132 Member States of the United Nations acting through a resolution of the UN General Assembly. But it was actually proposed, prepared and led by Vanuatu, and a group of Pacific Island Students Fighting Climate Change
Vanuatu
What were the questions at issue?
The questions put to the Court for its Advisory Opinion by the United Nations General Assembly were as follows:
”‘Having particular regard to the Charter of the United Nations, the International Covenant on Civil and Political Rights, the International Covenant on Economic, Social and Cultural Rights, the United Nations Framework Convention on Climate Change, the Paris Agreement, the United Nations Convention on the Law of the Sea, the duty of due diligence, the rights recognized in the Universal Declaration of Human Rights, the principle of prevention of significant harm to the environment and the duty to protect and preserve the marine environment,
(a) 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?-
(b) What are the legal consequences under these obligations for States where they, by their acts and omissions, have caused significant harm to the climate system and other parts of the environment, with respect to:
(i) States, including, 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?’”
How was it argued and who participated?
The list of countries, groups and organisations that submitted evidence or participated in proceedings underlines the high stakes international nature of the ruling, and worldwide awareness of its potential importance
“17. Within the time-limit as extended by the Order of the President of the Court dated 15 December 2023, written statements were filed in the Registry, in order of receipt, by
Portugal;
the Democratic Republic of the Congo;
Colombia;
Palau;
Tonga;
the Organization of the Petroleum Exporting Countries;
the International Union for Conservation of Nature;
Singapore;
Peru;
Solomon Islands;
Canada;
the Cook Islands;
Seychelles;
Kenya;
Denmark,
Finland,
Iceland,
Norway and Sweden (jointly);
the Melanesian Spearhead Group;
the Philippines;
Albania;
Vanuatu;
the Federated States of Micronesia;
Saudi Arabia;
Sierra Leone;
Switzerland;
Liechtenstein;
Grenada;
Saint Lucia;
Saint Vincent and the Grenadines;
Belize;
the United Kingdom of Great Britain and Northern Ireland;
the Kingdom of the Netherlands;
the Bahamas;
the United Arab Emirates;
the Marshall Islands;
the Parties to the Nauru Agreement Office;
the Pacific Islands Forum;
France;
New Zealand;
Slovenia;
Kiribati;
the Forum Fisheries Agency;
China;
Timor-Leste;
the Republic of Korea;
India;
Japan;
Samoa;
the Alliance of Small Island States;
the Islamic Republic of Iran;
Latvia;
Mexico;
South Africa;
Ecuador;
Cameroon;
Spain;
Barbados;
the African Union;
Sri Lanka;
the Organisation of African, Caribbean and Pacific States;
Madagascar;
Uruguay;
Egypt;
Chile;
Namibia;
Tuvalu;
Romania;
the United States of America;
Bangladesh;
the European Union;
Kuwait;
Argentina;
Mauritius;
Nauru;
the World Health Organization;
Costa Rica;
Indonesia;
Pakistan;
the Russian Federation;
Antigua and Barbuda;
the Commission of Small Island States on Climate Change and International Law;
El Salvador;
Bolivia;
Australia;
Brazil;
Vietnam;
the Dominican Republic;
Ghana;
Thailand;
Germany.
Pages 14-26 of the judgement are taken up with documenting all the advocates representing the different participating countries - Ministers, Ambassadors, Attorneys General, Professors. Up there with the Vanuatu delegation were Ralph Regenvanu, Special Envoy for Climate Change and the Environment, and Ms Cynthia Rosa Bareagihaka Houniuhi, Spokesperson, Activist, Pacific Island Students Fighting Climate Change.
What has the Court decided?
”The Court is of the view that the most directly relevant applicable law consists of the Charter of the United Nations, the UNFCCC, the Kyoto Protocol, the Paris Agreement, UNCLOS, the ozone layer treaties, the Biodiversity Convention, the Desertification Convention, the customary duty to prevent significant harm to the environment and the duty to co-operate for the protection of the environment, and international human rights law, as well as certain guiding principles for the interpretation of various applicable rules and principles (sustainable development, common but differentiated responsibilities and respective capabilities, equity, intergenerational equity, and the precautionary approach or principle).”
The actual terms of the Court’s findings are going to matter in the future, so it may be well to set them out. The Court:
“As regards question (a) put by the General Assembly:
A. Unanimously, Is of the opinion that the climate change treaties set forth binding obligations for States parties to ensure the protection of the climate system and other parts of the environment from anthropogenic greenhouse gas emissions. These obligations include the following:
(a) States parties to the United Nations Framework Convention on Climate Change have an obligation to adopt measures with a view to contributing to the mitigation of greenhouse gas emissions and adapting to climate change;
(b) States parties listed in Annex I to the United Nations Framework Convention on Climate Change have additional obligations to take the lead in combating climate change by limiting their greenhouse gas emissions and enhancing their greenhouse gas sinks and reservoirs;
(c) States parties to the United Nations Framework Convention on Climate Change have a duty to co-operate with each other in order to achieve the underlying objective of the Convention;
(d) States parties to the Kyoto Protocol must comply with applicable provisions of the Protocol;
(e) States parties to the Paris Agreement have an obligation to act with due diligence in taking measures in accordance with their common but differentiated responsibilities and respective capabilities capable of making an adequate contribution to achieving the temperature goal set out in the Agreement;
(f) States parties to the Paris Agreement have an obligation to prepare, communicate and maintain successive and progressive nationally determined contributions which, inter alia, when taken together, are capable of achieving the temperature goal of limiting global warming to 1.5°C above pre-industrial levels.
(g) States parties to the Paris Agreement have an obligation to pursue measures which are capable of achieving the objectives set out in their successive nationally determined contributions; and
(h) States parties to the Paris Agreement have obligations of adaptation and co-operation, including through technology and financial transfers, which must be performed in good faith;
B. Unanimously, is of the opinion that customary international law sets forth obligations for States to ensure the protection of the climate system and other parts of the environment from anthropogenic greenhouse gas emissions. These obligations include the following:
(a) States have a duty to prevent significant harm to the environment by acting with due diligence and to use all means at their disposal to prevent activities carried out within their jurisdiction or control from causing significant harm to the climate system and other parts of the environment, in accordance with their common but differentiated responsibilities and respective capabilities;
(b) States have a duty to co-operate with each other in good faith to prevent significant harm to the climate system and other parts of the environment, which requires sustained and continuous forms of co-operation by States when taking measures to prevent such harm;
C. Unanimously, is of the opinion that States parties to the Vienna Convention for the Protection of the Ozone Layer and to the Montreal Protocol on Substances that Deplete the Ozone Layer and its Kigali Amendment, the Convention on Biological Diversity and the United Nations Convention to Combat Desertification in Those Countries Experiencing Serious Drought and/or Desertification, Particularly in Africa, have obligations under these treaties to ensure the protection of the climate system and other parts of the environment from anthropogenic greenhouse gas emissions;
D. Unanimously, is of the opinion that States parties to the United Nations Convention on the Law of the Sea have an obligation to adopt measures to protect and preserve the marine environment, including from the adverse effects of climate change and to co-operate in good faith;
E. Unanimously, is of the opinion that States have obligations under international human rights law to respect and ensure the effective enjoyment of human rights by taking necessary measures to protect the climate system and other parts of the environment;
(4) As regards question (b) put by the General Assembly:
Unanimously, is of the opinion that a breach by a State of any obligations identified in response to question (a) constitutes an internationally wrongful act entailing the responsibility of that State. The responsible State is under a continuing duty to perform the obligation breached. The legal consequences resulting from the commission of an internationally wrongful act may include the obligations of:
(a) cessation of the wrongful actions or omissions, if they are continuing;
(b) providing assurances and guarantees of non-repetition of wrongful actions or omissions, if circumstances so require; and
(c) full reparation to injured States in the form of restitution, compensation and satisfaction, provided that the general conditions of the law of State responsibility are met, including that a sufficiently direct and certain causal nexus can be shown between the wrongful act and injury.”
What effect will the judgement have?
The Court has documented the history of UN resolutions, climate treaties and conventions, and it has spelled out the legal obligations of State Parties to each of them, thereby reinforcing the legal status of key climate treaties such as the Paris Agreement. These do not merely represent a scientific or political consensus at a particular time. They represent international law, and ultimately action can be taken based on that to establish the rights of other states.
The Court is further of the view that the relevant conduct for the purposes of these advisory proceedings is not limited to conduct that, itself, directly results in GHG emissions, but rather comprises all actions or omissions of States which result in the climate system and other parts of the environment being adversely affected by anthropogenic GHG emissions.
The Court accepts and recognises the consensus of climate science in general, and IPCC reports in particular, as representing the best available science on the causes, nature and consequences of climate change.
”The Court considers the 1.5°C threshold to be the parties’ agreed primary temperature goal for limiting the global average temperature increase under the Paris Agreement.”
In other words, not 2oC, or anything higher. The Court has taken note of parties’ subsequent commitments following the Paris Agreement, such as those given at the COP 26 climate talks, and applied best available science to say that these represent legal obligations.
“Climate change is a common concern. Co-operation is not a matter of choice for States but a pressing need and a legal obligation.”
The judgement is not confined to the key climate treaties and conventions and the legal obligations of State parties to those. It also reminds other states of their legal obligations under customary international law: the duty to prevent significant harm to the environment, the obligation to act with due diligence, and the duty to cooperate for the protection of the environment.
International human rights law
The judgement represents a major advance and consolidation of the links between a right to a clean environment, protection against climate change, and the operation of other human rights under other framework treaties and constitutions
“The Court is of the view that a clean, healthy and sustainable environment is a precondition for the enjoyment of many human rights, such as the right to life, the right to health and the right to an adequate standard of living, including access to water, food and housing. The right to a clean, healthy and sustainable environment results from the interdependence between human rights and the protection of the environment.
Consequently, in so far as States parties to human rights treaties are required to guarantee the effective enjoyment of such rights, it is difficult to see how these obligations can be fulfilled without at the same time ensuring the protection of the right to a clean, healthy and sustainable environment as a human right. The human right to a clean, healthy and sustainable environment is therefore inherent in the enjoyment of other human rights.
The Court thus concludes that, under international law, the human right to a clean, healthy and sustainable environment is essential for the enjoyment of other human rights.”
Corporations and continued production of fossil fuels
In part of the judgement relating to causation and remedies, the Court makes this statement, which will become much quoted by future litigants:
“Failure of a State to take appropriate action to protect the climate system from GHG emissions — including through fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licences or the provision of fossil fuel subsidies — may constitute an internationally wrongful act which is attributable to that State. The Court also emphasizes that the internationally wrongful act in question is not the emission of GHGs per se, but the breach of conventional and customary obligations identified under question (a) pertaining to the protection of the climate system from significant harm resulting from anthropogenic emissions of such gases.”
Conclusions:
“456. Before concluding, the Court recalls that it has been suggested that these advisory proceedings are unlike any that have previously come before the Court. At the same time, as the Court concluded earlier, the questions put to it by the General Assembly are legal ones … and the Court, as a court of law, can do no more than address the questions put to it through and within the limits of its judicial function; this is the Court’s assigned role in the international legal order.
However, the questions posed by the General Assembly represent more than a legal problem: they concern an existential problem of planetary proportions that imperils all forms of life and the very health of our planet. International law, whose authority has been invoked by the General Assembly, has an important but ultimately limited role in resolving this problem.
A complete solution to this daunting, and self-inflicted, problem requires the contribution of all fields of human knowledge, whether law, science, economics or any other.
Above all, a lasting and satisfactory solution requires human will and wisdom — at the individual, social and political levels — to change our habits, comforts and current way of life in order to secure a future for ourselves and those who are yet to come.
Through this Opinion, the Court participates in the activities of the United Nations and the international community represented in that body, with the hope that its conclusions will allow the law to inform and guide social and political action to address the ongoing climate crisis.”
Afterword about Vanuatu and Pacific Island students
The website of Pacific Island Students Fighting Climate Change has this to say about the case:
“It all began with 27 law students in the Pacific, who turned heartbreak into action. From a small classroom, we launched the #ClimateICJAO campaign, transforming our frustrations into purpose and a dream for justice into a global movement of solidarity.
We are demanding #ClimateJusticeAtTheICJ because for too long, those most responsible for the climate crisis have ignored their obligations, while our homes, cultures, identity - entire futures disappear.
We fight for our children, our homes, and for generations yet to come.”