International Court of Justice’s ruling on climate change affirms states’ obligations to human and planetary health

Over the past two years, we have seen a convergence of milestones on climate change. In summer 2024, the World Health Assembly adopted a dedicated resolution on climate change and health,1 followed by the Global Action Plan on Climate Change and Health 2025-2028, adopted at the 78th World Health Assembly in May 2025.2 Finally, and most notably, the International Court of Justice (ICJ) issued an advisory opinion in July 2025, which affirmed that states have binding legal obligations to prevent considerable environmental harm, cooperate in good faith to tackle climate change, and ensure that their nationally determined contributions under the Paris Agreement reflect the “highest possible ambition.”3 Ahead of COP30 in Belém, Brazil, which starts on the 10 November, this ruling provides a powerful reminder that climate justice and health equity are intertwined and that this intersection can act as a rare area of potential alignment between United Nations member states.

The ICJ’s opinion affirmed that countries have a legal duty to prevent serious environmental harm and to confront climate change. It described the climate crisis as an existential threat that directly endangers human rights and global equity. Crucially, the court made clear that governments are accountable not only for their own emissions but also for those of corporations operating within their borders. Although it stopped short of calling for a total phase-out of fossil fuels, it warned that approving or subsidising new oil, gas, or coal projects could breach international law. The ruling reaffirmed the heart of the Paris Agreement: the global pledge to keep temperature rise well below 2°C above pre-industrial levels and to pursue efforts to limit warming to 1.5°C, a threshold scientists warn is vital to protect health, livelihoods, and the planet’s life support systems.4

Even for countries that are not party to major climate treaties, the ICJ’s ruling is expected to shape national laws and judicial thinking. It adds weight to a growing body of legal precedent, from France and Germany56 to Brazil and the Philippines,78 where courts have ruled that governments have a duty to protect citizens from climate harm. Together, these decisions mark a shift in how climate action is understood: not as voluntary policy, but as a matter of legal responsibility and human rights protection. Over time, the ICJ opinion could help embed this principle into domestic law, transforming it from moral persuasion into binding national obligation.

The ruling aligns with growing momentum in the health sector to tackle the climate crisis, including the first “health day” at COP28 in Dubai in 2024 and the Global Conference on Climate and Health in Brazil in July 2025.910 Public health has long been a casualty of climate inaction, but these events reflect increasing global recognition that climate change is a health emergency.1112

At the heart of the climate crisis are the global economy’s consumption and production systems, which are rooted in extractivism, overconsumption, and the globalisation of supply chains. By placing a legal and ethical burden on high emitting countries to reduce domestic emissions and their global footprint, the ruling tackles the harms of these economic systems, including the damage caused by imported deforestation, outsourced pollution, and offshore fossil investments.

The ruling provides an opportunity to move towards a stronger understanding of and response to climate change, but substantial gaps in implementation remain.

At the global level, the ICJ ruling gives climate advocates a powerful new tool to push governments, but it doesn’t guarantee action because there are no global enforcement systems, and the right to a healthy environment has not reached the highest level of binding law. This leaves affected communities with limited legal recourse and hampers climate litigation efforts. To maximise its impact, governments and civil society actors could include the ruling in policy, litigation, and advocacy, helping to build the momentum needed for it to become a universal legal rule that binds all countries, which is consistently followed, even without a formal treaty.3

Regionally, across different countries, regulations remain inconsistent because of this lack of a binding authority. Although the ICJ ruling confirmed that states must regulate harmful corporate conduct, it stopped short of assigning companies direct legal responsibility. This gap enables fossil fuel and petrochemical industries to exploit legal grey areas and weaken global efforts, such as the plastics treaty. Regional human rights bodies should speak out when such actions undermine environmental and health rights. Governments must coordinate regulation to close these loopholes.13

Limited and uneven implementation of climate and health commitments leaves disadvantaged health systems unprepared, exposing deep inequities in meeting the ICJ ruling’s obligations. By affirming states’ duties to act on climate change and protect the right to a healthy environment, the ICJ provides a legal and moral lever to push for policies and investments that prevent climate shocks and build equity driven resilient health systems and societies. The UN and the Organisation for Economic Co-operation and Development (OECD) have continued to push for the adoption of structural solutions, including global tax justice mechanisms like the OECD/G20 base erosion and profit shifting framework, proposals for a UN tax convention, or taxes on the financial transactions of companies in the mining and oil and gas sectors to generate equitable climate finance and reduce the structural imbalances that constrain vulnerable countries.141516 These approaches aim to ensure that those with the greatest resources contribute more.

As countries prepare to unveil their revised climate commitments at COP30, governments have a chance to embed health equity at the heart of national climate strategies, linking clean air, resilient health systems, and sustainable urban design as shared goals. Tracking outcomes through system-wide indicators, such as service continuity and population resilience, will be key to accountability. Climate finance must follow suit, covering the real costs of health adaptation and prioritising investments that deliver co-benefits for people and the planet.

The ICJ opinion cements governments’ duty to act, framing the protection of health as a core legal obligation within climate action. Moving forward, governments should treat it as both a normative anchor and an advocacy lever to turn legal principle into policy reality.