While Europe continues to export fossil fuel infrastructure, subsidise polluters, and resist calls for loss and damage payments, the UN's highest court's decision has made it clear: inaction is illegal.

With that, Europe's colonial past comes into play. Some overseas territories of European countries, like those of France, the Netherlands and the UK, now face existential threats from rising seas and intensifying storms. With the legal groundwork laid, they may soon ask Europe for reparations.

The ICJ's ruling is a quiet legal revolution in international climate law. It makes clear that states are not free to act, or fail to act, without consequence.

According to the ruling, countries have binding legal obligations to cut their greenhouse gas emissions, protect human rights from climate-related harm, and align their national policies with science-based targets. Failure to meet these obligations can constitute an ”internationally wrongful act”, exposing governments to legal claims for restitution, compensation, or even cessation orders – legal demands to stop activities that cause further harm.

”This is a concern of planetary proportions that imperils all forms of life”, said ICJ president Judge Yuji Iwasawa.

The ICJ's advisory opinion doesn't create new treaties, but it interprets existing international law, including environmental principles, human rights law, and the Paris Agreement. The ruling is already being cited in courtrooms and is expected to shape future court decisions, reinforcing its authority far beyond The Hague.

And for those on the front lines of the climate crisis, like low-lying island nations, drought-stricken communities, and climate-displaced populations, the ruling offers something long denied: a path to justice.

The EU and its member states are among the world's top historic emitters – on average, Europeans emit nearly 70% more greenhouse gases per person than the world average. Since the Industrial Revolution, European countries have burned fossil fuels at an extraordinary scale, accounting for 22% of cumulative global emissions.

At the same time, many of the countries now suffering the worst climate impacts – Tuvalu, Vanuatu, Guyana, Mozambique – are former European colonies. And some territories still governed by European states, like French Polynesia or the Caribbean Netherlands, are among the most climate-vulnerable places on Earth. They have contributed little to the problem but are being hit hardest by rising seas, stronger storms, and food insecurity.

Europe's climate policies often promote lofty goals and moral leadership. But while it pledges action, it continues to export fossil fuel infrastructure, subsidise polluters, and stall efforts to deliver funding for climate-related ”loss and damage”. That contrast between words and action has long sparked criticism. Now, it opens the EU up to legal risk.

”Those who did the least to fuel this crisis deserve protection, reparations, and a future”, said Vishal Prasad of Pacific Islands Students Fighting Climate Change, one of the groups behind the push for the ICJ ruling.

Europe's reluctance to pay for past and present environmental harm will be, beyond hypocritical, legally indefensible.

Dr. Margaretha Wewerinke-Singh, an international sustainability law scholar, said the ICJ opinion strengthens the case for what she describes as legal decolonisation: ”It opens the door to claims – especially from vulnerable states and overseas territories – by confirming that countries can be held responsible for climate harm if they fail to meet their obligations”, she said to The European Correspondent. Legal success will still depend on proving a clear link between harm and state action, ”but that's increasingly possible. It's a major step toward accountability”.

What the Court delivered is, in effect, a recognition that climate justice cannot be separated from historical injustice. States that built their wealth on extractive economies and industrialisation – much of it driven by colonial expansion – must now reckon with their ongoing legal obligations to those they once ruled.

Even before the ICJ's landmark opinion, some European overseas territories were already challenging their parent states in court over climate inaction. In January 2024, Greenpeace Netherlands and residents of the Dutch-Caribbean island of Bonaire sued the Dutch government for failing to protect the island from climate impacts, with the case allowed to proceed by a Dutch court in September 2024. Similarly, in June this year, French NGOs challenged France's National Adaptation Plan for not adequately addressing vulnerabilities in overseas territories.

Overseas territories still under the authority of European states could, in theory, also bring claims against their parent states for failing to protect them from climate harm. While these cases would raise complex questions of standing and self-determination, the principle has now been legally articulated: even within hierarchical or postcolonial relationships, climate negligence is actionable.

The consequences of the ICJ opinion aren't limited to international lawsuits. Within Europe, the ruling could also undermine EU legislation that falls short of climate obligations, including the bloc's own flagship climate framework, the European Green Deal.

Under EU law, member states are required to reduce emissions by at least 55% by 2030 and reach net zero by 2050. But the ICJ's opinion raises the bar further, making clear that climate plans must represent the ”highest possible ambition” and align with the 1.5°C limit. Failing to do so could violate both political commitments and international legal obligations.

That puts growing pressure on the EU's current efforts to weaken or delay green legislation, particularly through the so-called Omnibus I package, which seeks to roll back parts of the Green Deal, including nature restoration and air pollution limits. Legal analysts warn that any drop in ambition could now face challenges in court and might even be ruled illegal.

”Every new law or climate plan will be measured against the 1.5°C limit”, said) David Frydlinger, partner at Cirio law firm. ”Unless EU policymakers bring strong proof that these plans are not weakening the EU's climate ambitions, they're likely to be struck down if challenged in court”.

The concern is echoed by climate finance expert Tsvetelina Kuzmanova of the University of Cambridge Institute for Sustainability Leadership: ”The current political trajectory in Brussels risks taking us at least a decade backwards”, she said, arguing the changes lag behind standards already set by leading companies.

In short, the ICJ has added legal teeth to what up until now were just moral arguments. Europe's climate policies will no longer be judged solely by Brussels – they're now being measured by international law.