From International Obligation to Domestic Duty: The ICJ Advisory Opinion and South Africa’s Second Nationally Determined Contributions

Abstract

Released in 2025, a year unprecedented in terms of the call on international and regional bodies for advisory opinions on obligations of states for climate action, the Advisory Opinion of the International Court of Justice (ICJ) on the Obligations of States in Respect of Climate Change 2025 represents a significant development in international climate law. The Opinion clarifies that States’ climate obligations arise not only from climate treaties such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement, but also from customary international law, human rights law, and general principles of international law, including due diligence, prevention of harm, equity, and intergenerational responsibility. As a result, climate action is increasingly viewed as a matter of legal obligation rather than political discretion. This study examines the extent to which South Africa’s Second Nationally Determined Contribution under the Paris Agreement (Second NDC) reflects the legal standards articulated by the ICJ. It argues that the Advisory Opinion strengthens the legal significance of Nationally Determined Contributions (NDCs) by transforming them from instruments of international cooperation into benchmarks for assessing state compliance with broader climate obligations. The study finds that South Africa possesses a relatively comprehensive legal framework capable of translating international climate obligations into domestic duties. Its Second NDC demonstrates a deliberate effort to implement these obligations through measurable mitigation targets, adaptation measures, loss and damage responses, and a commitment to a just transition. Nevertheless, questions remain regarding whether the level of mitigation ambition reflected in the NDC is sufficient to satisfy the due diligence, human rights, and intergenerational equity standards identified by the ICJ, particularly considering South Africa’s continued dependence on coal and the objective of limiting global warming to 1.5 °C. The study concludes that the ICJ Advisory Opinion has strengthened climate accountability by providing legal benchmarks against which domestic climate action may increasingly be assessed, challenged, and enforced.