Legal experts from the International Union for Conservation of Nature (IUCN) have underscored that States hold binding obligations under international law to protect the climate system. This assertion was made during the landmark climate hearings at the International Court of Justice (ICJ), which concluded oral proceedings on December 13, 2024.
Representing nearly 100 States and 12 international organizations, the ICJ hearings were initiated following a 2023 request by the UN General Assembly for an Advisory Opinion on States’ legal responsibilities regarding climate protection. The proceedings marked a historic moment for the ICJ as it addressed climate change for the first time.
IUCN’s legal experts highlighted that climate obligations are rooted not only in global climate treaties like the Paris Agreement but also in other international agreements on human rights, biodiversity, and maritime law, as well as customary international law.
“Every State has an obligation under international law to reduce greenhouse gas emissions in line with the 1.5°C warming threshold and to reverse any overshoot,” stated Prof. Christina Voigt, Chair of the IUCN World Commission on Environmental Law, during the hearings.
The organization, representing both State and non-State actors, emphasized that breaching these obligations could carry serious legal consequences. According to Prof. Voigt, States must submit and adhere to national climate commitments under the Paris Agreement and ensure their actions do not harm the environment of other States, as per customary international law.
Prof. Francesco Sindico, Co-chair of IUCN’s Climate Change Law Specialist Group, elaborated on potential repercussions for non-compliance. “States would need to enforce necessary measures to meet their climate obligations, prevent further breaches, and make full reparations, including restitution or compensation,” he explained.
Dr. Grethel Aguilar Rojas, IUCN’s Director General, called the Advisory Opinion pivotal for addressing the climate crisis. “This ruling can send a strong message to those most vulnerable to climate change impacts—indigenous peoples, migrants, women, children, and the natural world. It emphasizes the urgent need for deep, rapid, and sustained emissions reductions,” she noted.
Although the ICJ’s Advisory Opinion, expected in 2025, will not be legally binding, it is anticipated to carry significant influence. The ruling is poised to shape global climate action, foster accountability, and bolster international cooperation, paving the way for a more sustainable future.
With IUCN’s participation highlighting the fusion of legal expertise and environmental advocacy, this case marks a critical step in holding States accountable for their climate commitments.
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