The ICJ’s 2025 Climate Change Advisory Opinion: Critical Implications for UK Environmental and Planning Law

On 23 July 2025, the International Court of Justice (ICJ) delivered a historic Advisory Opinion on the Obligations of States in respect of Climate Change. This long-awaited opinion – requested by a UN General Assembly resolution led by climate-vulnerable states – represents the first authoritative clarification by the ‘world court’ of states’ legal duties concerning climate change. It addresses two fundamental questions: (a) the obligations of states under international law to protect the climate system from anthropogenic greenhouse gas (GHG) emissions, for present and future generations; and (b) the legal consequences if states, by their acts or omissions, cause significant climate harm, particularly to vulnerable states, peoples, and individuals. While advisory in nature and not directly binding, the opinion carries significant weight as an expression of international law. Its sweeping findings have deployable relevance in domestic courts worldwide, potentially opening a new front in climate change litigation and policy-making.