“[T]he 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. … [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.” 

International Court of Justice, Advisory Opinion on Obligations of States in Respect of Climate Change dated July 23, 2025 [456].

Introduction

This was followed by a written phase of proceedings, where 153 written statements and comments were filed by states and international organisations. Public hearings were conducted from December 2–13, 2024, during which 107 states and international organisations presented oral statements, reflecting the highest level of participation in a proceeding in the history of the ICJ.

On July 23, 2025, the ICJ issued an advisory opinion on these matters. The operative clause of the opinion was adopted unanimously, although several judges appended separate opinions on aspects of the advisory opinion. 

The obligations of states under international law to ensure the protection of the climate system 

Climate change treaties

The ICJ examined the obligations of states under the climate change treaty framework, considering the United Nations Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol and the Paris Agreement to be the principal legal instruments regulating the international response to the global problem of climate change. The UNFCCC establishes the overarching objectives and principles, while the Kyoto Protocol and Paris Agreement set out more detailed and interrelated obligations.

Under these treaties, states have mitigation, adaptation and co-operation and assistance obligations:

• Mitigation: States must take steps such as limiting GHG emissions by sources and enhancing sinks and reservoirs of GHGs.
• Adaptation: States must adjust to actual or expected climate change and its effects in order to moderate harm or exploit beneficial opportunities.
• Co-operation and assistance: States must work together in good faith (e.g. by financial transfers, technology transfers and capacity-building).