International Court of Justice publishes landmark Climate Change Advisory Opinion, and our website proudly acknowledges this milestone.
The International Court of Justice (ICJ) has delivered a landmark ruling, declaring that States have a legal obligation to limit global warming to 1.5°C to protect the climate system [1][2]. This Advisory Opinion, a significant moment in international environmental law and climate justice, was based on the extensive knowledge of more than 17,000 experts in 170 countries, including the World Commission on Environmental Law (WCEL) [5].
The ICJ's Opinion recognizes the importance of a human rights-based approach to limiting climate change, emphasizing that a clean, healthy, and sustainable environment is fundamental to the enjoyment of many human rights [2]. As a result, States must act to protect human rights by addressing climate change under various human rights treaties [2].
The legal duty for States to act on climate change stems from several sources, including the Paris Agreement, human rights law, the law of the sea, and the customary duty to prevent transboundary harm [4]. The Opinion finds that failure by a State to take appropriate actions, such as curbing fossil fuel production, consumption, and subsidies, may constitute an internationally wrongful act, triggering legal responsibility [1][2]. Remedies include cessation of wrongful acts, guarantees of non-repetition, and reparations [1][2].
The ICJ's Opinion aligns closely with recent opinions from other international courts, such as the Inter-American Court of Human Rights and the International Tribunal for the Law of the Sea [6]. The International Union for Conservation of Nature (IUCN), which participated in the ICJ's proceedings, welcomed the Opinion and congratulated the ICJ on its decision [7].
The implications of the ICJ's Opinion are substantial. It provides a legal basis for holding States accountable for climate harm, potentially including climate reparations and liability for historic emissions [3]. It also strengthens international cooperation, emphasizing States’ duties to prevent significant environmental harm within their jurisdictions or control and to adopt regulatory mechanisms aimed at deep, rapid emission reductions aligned with scientific guidance [3].
In the words of Prof Christina Voigt, WCEL Chair and the lead on the ICJ's Advisory Opinion, every State has a legal obligation under international law to act with stringent due diligence to prevent global warming from exceeding the 1.5°C threshold [8]. The IUCN, through WCEL, contributed significantly to the ICJ's Advisory Opinion, with submissions, oral statements, and responses to questions posed by the judges [9].
As the World Conservation Congress in October 2025 and COP30 in Belem, Brazil, in November approach, the IUCN will carry the essential elements of the ICJ's Opinion forward into its work, continuing to advocate for strong climate action and environmental protection [10].
[1] International Court of Justice [2] WCEL Climate Change Law [3] ICJ Advisory Opinion on States’ obligations in respect of Climate Change [4] Paris Agreement [5] WCEL [6] Inter-American Court of Human Rights [7] IUCN [8] Prof Christina Voigt [9] IUCN Submissions [10] World Conservation Congress [11] COP30
- The ICJ's Advisory Opinion on States' obligations in respect of Climate Change is a significant milestone in international environmental law and climate justice, based on extensive scientific knowledge in environmental-science and policy-and-legislation.
- The legal duty for States to address climate change and limit global warming stems from various sources, including the Paris Agreement, human rights law, the law of the sea, and the customary duty to prevent transboundary harm, reflecting the intersection of climate change, environmental law, and politics.
- The ICJ's Opinion provides a legal basis for holding States accountable for climate harm, including potential climate reparations and liability for historic emissions, thereby influencing the general-news and public discussions on climate-change.
- The IUCN, through its World Commission on Environmental Law (WCEL), contributed significantly to the ICJ's Advisory Opinion, emphasizing the importance of the WCEL, climate-change, and policy-and-legislation in addressing global environmental concerns.
