What Does the International Court of Justice Advisory Opinion on Climate Change Mean for Multilateral Environmental Agreements?

This policy brief analyzes the July 2025 International Court of Justice (ICJ) Advisory Opinion on the Obligations of States in Respect of Climate Change, specifically focusing on how it affects the implementation of Multilateral Environmental Agreements (MEAs). The document argues that the ICJ rejected the 'lex specialis' doctrine, ruling instead that climate obligations are integrated with other environmental treaties, human rights law, and customary international law.

• The ICJ rejected the 'lex specialis' argument—which claimed only the UN climate regime creates legal obligations—and instead adopted the principle of systemic integration. This means the UN climate regime and other Multilateral Environmental Agreements (MEAs), human rights law, and customary international law mutually inform and reinforce each other and must be implemented in a coherent, integrated manner.
• States are required to integrate climate considerations when implementing obligations under specific MEAs, including the Convention on Biological Diversity (CBD), the UN Convention to Combat Desertification, the UN Convention on the Law of the Sea, and the Vienna Convention for the Protection of the Ozone Layer and its Montreal Protocol. Implementation measures that ignore climate risks or cause additional climate harm are no longer considered compliant under international law.
• The ICJ linked climate action to human rights, stating that human rights obligations are not fulfilled if a state fails to act on climate mitigation and adaptation. The court identified the right to a clean, healthy, and sustainable environment as a precondition for other rights, including the right to life, health, privacy, and the rights of women, children, and Indigenous Peoples.
• Actions taken under MEAs can serve as evidence of a state's 'due diligence' in meeting climate obligations. For example, implementing Target 8 of the CBD's Kunming-Montreal Global Biodiversity Framework to minimize climate change impacts on biodiversity can be used as evidence of due diligence under the Paris Agreement.
• The Advisory Opinion clarifies that the status of a state as 'developed' or 'developing' is not static but depends on evolving 'national circumstances.' This allows states to 'graduate' into the developed country category, which triggers new binding legal obligations, such as assisting vulnerable countries with adaptation and increasing efforts to meet the 1.5ºC temperature goal.

APA

Kosolapova, E. (2026). What Does the International Court of Justice Advisory Opinion on Climate Change Mean for Multilateral Environmental Agreements? International Institute for Sustainable Development. https://www.iisd.org/system/files/2026-03/icj-advisory-opinion-multilateral-environmental-agreements.pdf

Chicago

Kosolapova, Elena. What Does the International Court of Justice Advisory Opinion on Climate Change Mean for Multilateral Environmental Agreements? International Institute for Sustainable Development, 2026. https://www.iisd.org/system/files/2026-03/icj-advisory-opinion-multilateral-environmental-agreements.pdf.

Wikipedia

{{cite report |last1=Kosolapova |first1=Elena |title=What Does the International Court of Justice Advisory Opinion on Climate Change Mean for Multilateral Environmental Agreements? |publisher=International Institute for Sustainable Development |date=March 2026 |url=https://www.iisd.org/system/files/2026-03/icj-advisory-opinion-multilateral-environmental-agreements.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{kosolapova2026what, author = {Kosolapova, Elena}, title = {{What Does the International Court of Justice Advisory Opinion on Climate Change Mean for Multilateral Environmental Agreements?}}, institution = {International Institute for Sustainable Development}, year = {2026}, month = mar, url = {https://www.iisd.org/system/files/2026-03/icj-advisory-opinion-multilateral-environmental-agreements.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }