On 23 July 2025, the International Court of Justice (ICJ) issued its Advisory Opinion (AO) on Obligations of States in Respect of Climate Change, providing the most authoritative interpretation to date of States' obligations under international law in responding to climate change. The ICJ-AO is more than a legal milestone. It provides greater clarity about how existing obligations under international climate and environmental law apply in practice, reinforcing the importance of healthy ecosystems, science-based decision making, cooperation, and long-term resilience.
This handbook has been developed to help island governments, practitioners, Indigenous Peoples, community organisations, educators, researchers, and young leaders understand what the Advisory Opinion means for islands and how it may inform practical action. Although the Advisory Opinion is directed to States, many of its implications extend to island jurisdictions, territories, municipalities, and the institutions responsible for managing land, freshwater, coastal, and marine environments. The handbook therefore focuses on implementation, recognising that many of the actions needed to strengthen climate resilience occur at the local and regional levels. This publication is not intended to provide legal advice or a comprehensive commentary on the Advisory Opinion. Instead, it explains the Court's reasoning in plain language, highlights where biodiversity and healthy ecosystems fit within the Court's analysis, and identifies practical opportunities for islands to strengthen existing climate action.