International Court of Justice (ICJ): On 23-7-2025, The 14-Judge Bench of the ICJ issued its Advisory Opinion on Obligations of States in respect of Climate Change. The United General Assembly on 29-3-2023 had requested the ICJ to give its opinion on the following questions:
(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, and particularly, 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?
Background:
UN General Assembly via resolution 77/276, requested the ICJ to issue opinion on the abovementioned issues referring to Article 65 of the Statute of the Court. The request for an advisory opinion was transmitted to the Court by the Secretary-General of the United Nations. During the proceedings, 91 written statements and 62 written comments were filed in the Registry by States and international organizations. The Court held public hearings in the proceedings during which 96 States and 11 international organizations presented oral statements, which made these proceedings having the highest level of participation in a proceeding in both the history of ICJ and its predecessor- the Permanent Court of International Justice1.
Court’s Assessment:
The Court unanimously opined that that it had the jurisdiction to give the advisory opinion requested. As regards to the questions posed before it, the ICJ explained that it has been only called upon to firstly establish the applicable legal framework of State responsibility in respect of States that have breached their obligations to protect the climate system; and, second, to outline in general terms the legal consequences flowing therefrom.
The ICJ further found that the principle of lex specialis does not lead to a general exclusion by the climate change treaties of other rules of international law.
The ICJ further observed that while climate change is caused by cumulative greenhouse gas emissions, it is scientifically possible to determine each State’s total contribution to global emissions, taking into account both historical and current emissions. What constitutes a wrongful act is not the emissions in and of themselves, but actions or omissions causing significant harm to the climate system in breach of a State’s international obligations.
The ICJ further stated that UN Framework Convention on Climate Change and Paris Agreement seek to protect the essential interest of all States in safeguarding the climate system, which benefits the entire international community. As such, the obligations of States under these treaties are obligations erga omnes partes. As a result, all States parties have a legal interest in the protection of the main mitigation obligations set forth in the climate change treaties and may invoke the responsibility of other States for failing to fulfil them.
As for the legal consequences arising from wrongful acts, the ICJ found that it cannot, in the context of these advisory proceedings, specify precisely what consequences are entailed by the commission of an internationally wrongful act of breaching obligations to protect the climate system from anthropogenic greenhouse gas emissions, since such consequences depend on the specific breach in question and on the nature of the particular harm.
Advisory Opinion:
In a significant moment, the ICJ bench comprising of President Iwasawa; Vice-President Sebutinde; and Tomka, Abraham, Yusuf, Xue, Bhandari, Nolte, Charlesworth, Brant, Gómez Robledo, Cleveland, Aurescu, Tladi, JJ., were unanimous in adopting the Advisory Opinion on the questions raised by UN General Assembly.
Answering Question (a)
The climate change treaties set 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:
(i) 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;
(ii) States parties listed in Annexure 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;
(iii) States parties to the United Nations Framework Convention on Climate Change have a duty to co-operate with each other to achieve the underlying objective of the Convention;
(iv) States parties to the Kyoto Protocol must comply with applicable provisions of the Protocol;
(v) 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;
(vi) 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;
(vii) 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;
(viii) States parties to the Paris Agreement have obligations of adaptation and cooperation, including through technology and financial transfers, which must be performed in good faith.
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:
(i) 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;
(ii) 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.
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.
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.
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.
Answering Question (b):
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:
- Cessation of the wrongful actions or omissions, if they are continuing
- Providing assurances and guarantees of non-repetition of wrongful actions or omissions, if circumstances so require
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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.
[Obligations of States in respect of Climate Change, In re, General List No. 187, decided on 23-7-2025]
