SEO Riders:
– ICJ affirms binding duties under treaties and customary law to prevent climate harm.
– Nationally Determined Contributions legally binding; failure may trigger state responsibility.
– Opinion opens door to reparations, litigation, and human rights claims over environmental damage.
The International Court of Justice (ICJ) issued a unanimous advisory opinion on 23 July 2025, affirming that under both treaty-based and customary international law, states have a binding obligation to prevent significant harm from greenhouse gas emissions and to cooperate globally in addressing climate change. The Court explicitly recognized that a clean, healthy, and sustainable environment is a human right, and determined that Nationally Determined Contributions (NDCs under the Paris Agreement are legally binding instruments, subject to stringent due diligence requirements aligned with the goal of limiting warming to 1.5 °C. Even states that are not parties to key treaties like the UNFCCC are now considered bound under customary obligations to take action to mitigate climate harm.
The opinion further clarifies that failure to comply with these duties—including maintaining NDCs, regulating fossil fuel subsidies, or approving fossil fuel expansion—could constitute an internationally wrongful act, triggering legal consequences such as cessation, guarantees of non-repetition, and full reparations via restitution or compensation. For the first time under international law, climate obligations are reasserted as erga omnes—meaning any state may hold another state accountable for breaches—even in cases involving historical or cumulative emissions. Experts view the ruling as a paradigm shift, providing legal grounding for climate litigation, reparations claims, and enhanced climate justice frameworks globally.
