ICJ: States Legally Bound to Tackle Climate Threat

The International Court of Justice (ICJ) issued a landmark advisory opinion on July 23, declaring climate change an “urgent and existential threat” and affirming that states have legally binding obligations under international law—including human rights treaties—to reduce greenhouse gas emissions (GHG) and protect vulnerable populations. 

A unanimous panel of 15 judges, led by ICJ President Judge Yuji Iwasawa, ruled that failure to act on climate change “may constitute an internationally wrongful act.” Iwasawa emphasized that states must “cooperate to achieve concrete emission reduction targets” and that access to “a clean, healthy and sustainable environment” is a human right essential to the enjoyment of all other rights.

Greenpeace hailed the decision as historic, stating it obliges governments to regulate not only public activities but also private-sector emissions. Danilo Garrido, legal counsel at Greenpeace International, called it “the start of a new era of global climate accountability.”

The Court outlined three urgent priorities: reducing fossil fuel production and consumption, rapidly expanding renewable energy, and ensuring transparent sharing of climate data. These priorities echo obligations under existing international agreements such as the UNFCCC, Kyoto Protocol, and Paris Agreement.

The opinion followed a request from the UN General Assembly, which asked the Court to clarify states’ legal responsibilities in addressing climate change and the consequences of failing to meet them. The request was driven by a 2019 initiative led by Vanuatu and supported by other Pacific Island nations facing existential threats from rising sea levels.

Vanuatu’s Climate Minister, Ralph Regenvanu, described the ruling as “a crucial course correction in this critically important time.” Earlier this year, Australia introduced a climate visa for citizens of Tuvalu, enabling up to 280 residents per year to relocate due to rising sea levels. More than a third of Tuvaluans have already applied, as projections indicate the island could become uninhabitable by the century’s end.

Although advisory, the ICJ’s opinion carries considerable legal and political weight. Experts say it may open the door to reparations claims by countries harmed by climate inaction. The Court noted that legal consequences could include financial compensation for climate-related losses, and even the immediate suspension of emissions that exceed certain limits. Garrido emphasized: “The Court’s message is clear: the production, consumption, and subsidization of fossil fuels may violate international law. Polluters must stop and must pay.”

The ruling could have far-reaching implications for high-emitting countries such as the US and Mexico, both of which have historically resisted discussions on climate reparations during negotiations under the UNFCCC and Paris Agreement. The Court rejected the idea that these agreements serve as the sole legal framework for climate action and stated that merely submitting Nationally Determined Contributions (NDCs) is not enough. If a country’s NDC is insufficient to meet the Paris Agreement’s 1.5°C goal, it cannot be considered legally adequate.

This comes just months after the Mexican government announced a new climate plan, NDC 3.0. Yet, according to Guillermo Gomez, CEO, sustainability consultancy G2H, “Mexico’s policies have consistently fallen short of past NDCs. Current targets—such as a 35% emissions cut by 2030—lack credible plans, funding, or accountable institutions.” He argues that unless this changes, NDC 3.0 is unlikely to shield Mexico from future liability under the ICJ’s opinion.

Mexico also faces legal scrutiny from a 2024 ruling by the Inter-American Court of Human Rights, which declared that climate change constitutes a human rights emergency. That decision—previously the most progressive on climate law—gave climate-related harm the same legal weight as torture or genocide. The ICJ’s opinion now builds on and reinforces that precedent, establishing a new global standard for climate accountability.