THE HAGUE — Following the initiative led by Vanuatu through UN General Assembly Resolution 77/276, the International Court of Justice delivered its Advisory Opinion on the Obligations of States in Respect of Climate Change.
The opinion clarifies the relationship between multilateral climate treaties, international human rights obligations, and customary rules of state responsibility.
1. Customary Due Diligence and the No-Harm Rule
A central procedural issue concerned the applicable standard of review: several major emitting states argued that the UN Framework Convention on Climate Change (UNFCCC) and the Paris Agreement operate as lex specialis, limiting state duties to procedural pledges contained in nationally determined contributions (NDCs).
The Court confirmed the concurrent application of customary rules:
- The Obligation to Prevent Significant Harm: The customary no-harm rule (Trail Smelter, Corfu Channel, Pulp Mills) applies directly to transboundary environmental injury caused by greenhouse gas emissions.
- Objective Standard: Meeting procedural NDC reporting obligations under the Paris Agreement does not create an automatic safe harbor against breaches of customary due diligence. Due diligence is an objective standard of conduct requiring states to implement regulatory and enforcement measures informed by scientific consensus.
2. Human Rights Obligations and Attribution Under ARSIWA
The Court affirmed the direct link between significant atmospheric degradation and the impairment of fundamental human rights, including rights to life, health, culture, and means of subsistence.
Addressing state responsibility for cumulative transboundary harm:
- Regulatory Responsibility: While greenhouse emissions originate from diverse private and state actors, a state incurs responsibility under international law when it fails to adequately regulate or mitigate activities within its jurisdiction or control.
- Composite Acts: Drawing on Articles 14 and 15 of the ILC Articles on State Responsibility, prolonged regulatory failure constitutes a continuous wrongful act, providing a doctrinal foundation for assessing state compliance before international dispute settlement bodies.