On July 23, 2025, the International Court of Justice (ICJ) issued a landmark advisory opinion, holding that nation-states have obligations under international law to mitigate greenhouse gas (GHG) emissions, adapt to the effects of climate change and cooperate in good faith with one another to prevent harm to the climate and environment. If a state fails to meet these duties, the ICJ may conclude it conducted a "wrongful act", and injured states may be entitled to reparations for that wrongful act. Small island nations advocated for the ICJ opinion, which was opposed by major emitting states including the United States (under the Biden administration), China, Saudi Arabia and the European Union (EU). The ICJ opinion introduces a new element to an already complex web of environmental obligations for states, corporations and institutions. While the ICJ advisory opinion is not binding upon state governments, including the United States, it provides persuasive authority to tribunals faced with similar legal questions and provides a backdrop for international customs, which may influence legal obligations. For example, courts in the United States now will need to grapple with U.S. Environmental Protection Agency's (EPA) proposal to revoke the endangerment finding associated with GHG emissions from mobile and stationary sources. Non-governmental organizations, interest groups and other nations may seek to use the legal analysis of the ICJ advisory opinion in future litigation against governments or private companies, though such legal strategies have not garnered much success in United States federal courts.
ICJ Advisory Opinion
In its July 23, 2025, advisory opinion, the ICJ ruled that international law requires states to prevent significant harm to the environment and climate system and to cooperate in good faith to mitigate and adapt to climate change. The case began in 2021 when a coalition of small island nations, led by Vanuatu, sought an advisory opinion from the ICJ on states' climate obligations. In 2023, the court adopted a resolution to consider two questions:
- 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 where they, by their acts and omissions, have caused significant harm to the climate...
