The 2025 International Court of Justice Advisory Opinion on <i>Obligations of States in respect of Climate Change</i>

Abstract The 2025 International Court of Justice Advisory Opinion on Obligations of States in respect of Climate Change constitutes a diligent and reasoned exposition of the main bodies of international law on climate change. The Court read this law harmoniously and clearly identified States’ obligations as well as the legal consequences of breach. Under both treaty and customary international law, States must act with due diligence and do their utmost to mitigate climate change, including through action on fossil fuel production and consumption. The Court confirmed that the law of State responsibility applies if States fail to fulfil their obligations, and sketches a pathway for establishing causation of harm that would become relevant if reparation were sought. This article examines the key dimensions of the Advisory Opinion, including the applicable law identified by the Court and its analysis of State responsibility, informing readers of the Court’s main findings and their consequences. It also puts forward a few reflections, including on the Advisory Opinion’s emphasis on international cooperation and finance flows, the Court’s views on sea-level rise and self-determination, the role of science in the Advisory Opinion and what the Court left for the future.