On July 23, 2025, the International Court of Justice (ICJ) issued an landmark Advisory Opinion on climate change, reaffirming that all States have binding legal obligations to act on climate change. This decision, although not binding as a judgment, marks a pivotal moment in international law and opens the door for liability for climate inaction to be enforced in national and international courts.
What led to this historical decision did not originate in government offices, but on the shores of the Pacific. In 2019, a group of young activists and law students from Pacific Island nations like Vanuatu and Tuvalu founded the Pacific Islands Students Fighting Climate Change collective. Following its creation, the group launched a diplomatic and legal campaign asking the ICJ to rule on the legal responsibilities of states in the fight against climate change. Their initiative received growing support from governments, civil society organizations and indigenous communities. Finally, on March 29, 2023, the United Nations General Assembly adopted Resolution A/RES/77/276, driven by Vanuatu, which formally requested an Advisory Opinion from the ICJ on two questions:
- What are the obligations of States under international law to ensure the protection of the climate system and other parts of the environment from anthropogenic emissions of greenhouse gases for States and for present and future generations;
- What are the legal consequences under these obligations for States where they, by their acts and omissions, have caused significant harm to the climate system and other parts of the environment, with respect to:
- States, including small island developing States, which due to their geographical circumstances and level of development, are injured or specially affected by or are particularly vulnerable to the adverse effects of climate change?
- Peoples and individuals of the present and future generations affected by the adverse effects of climate change?
This resolution, voted without opposition, was a key step in opening a new stage in international climate justice. Two years later, after receiving over 90 submissions from states and organizations, the Court published its response.
A Legal Obligation
The Court made it clear that States' climate obligations are not limited to multilateral environmental agreements such as the United Nations Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol or the Paris Agreement. In paragraph 171 of the Opinion, the ICJ rejected the argument based on the lex specialis principle, where some states argued that climate obligations could only be interpreted within the specific framework of these treaties. Instead, the court found that States' commitments are also governed by other branches of international law, such as customary international law, human rights, the law of the sea and other legal instruments.
One of the most relevant aspects of the decision is that the Court considered that the objective of limiting global warming to 1.5°C is legally binding, not simply a political goal (para. 224). This implies that States must adjust their national policies and emissions levels in line with this target, the best available science, and the principles of equity and common but differentiated responsibilities and respective capabilities.
Reparations, Responsibilities and the End of Impunity
Another key element of the Opinion is that States that fail to comply with their climate obligations may be held legally responsible for the damages caused. Paragraphs 450 to 454 states that these responsibilities may include restitution, financial compensation, or symbolic reparation. This could apply both to tangible damage, such as infrastructure destroyed by hurricanes or eroded coastlines, and to ecological, social and cultural losses.
In a particularly relevant statement for the future of the energy sector (paragraph 427), the Court warned that States could also be responsible if they do not adequately regulate the production, consumption and subsidies of fossil fuels, or if they continue to grant hydrocarbon exploration licenses. This statement puts extractive companies and the governments that facilitate their expansion at the center of the debate.
Furthermore, the Court directly addressed the role of large emitters. It pointed out in paragraph 315 that even states that have withdrawn from the Paris Agreement - as was the case with the US in the past - are legally bound to reduce their emissions under customary international law. It also clarified in paragraph 226 that countries such as China and India cannot indefinitely hide behind their status as “developing countries” to avoid responsibilities, as their status depends on current, not historical, circumstances.
A Victory for Climate Justice
The Court's decision was greeted with optimism by environmental organizations, Global South leaders and youth activists. For many, it represents a turning point in the construction of an international legal regime that effectively protects vulnerable populations and the planet. Although the opinion has no immediate binding effect, its value as a precedent and as a guide for future litigation and policy decisions is enormous.
UN General Secretary António Guterres welcomed the decision with enthusiasm, stating that “[the publication] is a victory for our planet, for climate justice and for the power of young people to make a difference”. Guterres stressed that the process was initiated by Pacific students who decided not to resign themselves to silence in the face of the climate threat: “Pacific youth started this call, and the world must respond”.
Indeed, this advisory opinion represents much more than a legal text: it is the result of a groundbreaking grassroots campaign driven by those who have contributed least to the climate crisis but are among those who suffer the most. Its legacy is a powerful reaffirmation that international law not only can but must serve climate justice.
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