The International Court of Justice (ICJ) has delivered a landmark advisory opinion affirming that states have legal obligations under international law to act against climate change.

Clarifying State Responsibilities

• Advisory Opinion as Legal Clarification: Although non-binding, ICJ’s advisory opinion serves as an authoritative interpretation of international law and strengthens accountability by influencing state behaviour through legal and moral pressure.
• Binding Nature of Climate Obligations: The Court ruled that states must exercise due diligence and cooperate in fulfilling their Nationally Determined Contributions (NDCs) under the Paris Agreement, which must reflect their highest possible ambition.
• Global Scientific Consensus Upheld: The Court reinforced the 1.5°C temperature limit as the operative standard for climate mitigation, using the best available scientific evidence and Conference of Parties (COP) decisions to interpret treaty obligations.

Principles of Climate Justice and Differentiation

• Recognition of CBDR-RC Principle: The ICJ reiterated the principle of Common But Differentiated Responsibilities and Respective Capabilities (CBDR-RC), allowing differentiated obligations based on historical emissions, development level, and national capacity.
• Legal Duty of Climate Finance: Developed nations were held to a legally binding obligation to provide financial support and technology transfer to developing countries for mitigation and adaptation, subject to good faith and due diligence.
• Rights-Based Climate Action: The Court linked climate change to human rights obligations, particularly for vulnerable populations, and emphasised that mitigation policies must align with the goal of achieving a just and inclusive green transition.

Broader Legal and Strategic Implications

• Rejection of Self-Contained Regime Argument: The ICJ dismissed the argument that climate treaties are self-contained and clarified that obligations also arise from customary international law, environmental treaties, and the Law of the Sea Convention.
• Attribution of Emissions Responsibility: The Court affirmed that individual state responsibility is valid, as scientific methodologies can accurately estimate each country's contribution to climate change through historical and current emissions data.
• Empowerment of the Global South: Small island nations initiated this process, and the opinion enhances their ability to demand climate justice, support strategic litigation, and push the Global North towards meeting climate finance commitments.

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