Advisory Opinion on Obligations of States in Respect of Climate Change (I.C.J.)

Abstract On July 23, 2025, the International Court of Justice delivered a unanimous advisory opinion on the Obligations of States in respect of Climate Change, the third opinion on climate change from an international judicial body. Requested by consensus by the UN General Assembly in 2023, the proceedings drew unprecedented participation from ninety-six states and eleven international organizations. In the Opinion, the Court confirmed its advisory jurisdiction over the legal questions posed and found no compelling reason to decline the request. It identified the “most directly relevant applicable law” as the climate change treaties, UNCLOS, other environmental treaties, customary international law, and international human rights law, and held that the climate change treaties are not lex specialis . The Court affirmed obligations under the Paris Agreement to pursue the 1.5°C “primary temperature goal” and that there were limits to parties’ discretion in formulating their nationally determined contributions. Drawing on its prior decisions, the Court held that the customary duty to prevent significant environmental harm applies to the climate system under a stringent due diligence standard, and recognized cooperation as a legal obligation rather than a matter of choice. On sea-level rise, it found no obligation to update maritime baselines that were established in conformity with UNCLOS and concluded that statehood persists despite the loss of a constituent element. On legal consequences, the Court applied the customary law of state responsibility and observed that the entire panoply of legal consequences could apply to breaches, but indicated that particularized remedies would be fact-specific.