The World Court Has Spoken on Climate. The Harder Question Is Who Pays.

On 28 May 2025, the Higher Regional Court of Hamm, in North Rhine-Westphalia, dismissed a claim that had been before the German courts for almost ten years. The claimant, Saúl Luciano Lliuya, is a farmer and mountain guide from Huaraz, a city in the Peruvian Andes that lies below Lake Palcacocha, a glacial lake swollen by meltwater. The defendant was RWE, one of Germany’s largest energy companies.

The claim was modest in money and large in principle. Lliuya argued that emissions from RWE’s power plants had contributed to global warming, that warming had increased the risk of the lake overflowing and flooding his home, and that RWE should therefore bear a share of the cost of protecting it. The share he proposed matched RWE’s estimated contribution to historical global emissions: a little under half of one percent.

RWE disputed that a single company could be held liable under private law for a phenomenon produced by emissions from every country on earth over two centuries. The court of first instance in Essen had agreed with RWE and dismissed the claim in 2016. On appeal, the Hamm court took a different view of the law, admitted the case to the evidence stage, and in 2022 judges and court-appointed experts travelled to Huaraz to inspect the site.

The judgment of 2025 contained two findings that pointed in opposite directions.

On the law, the court accepted the claimant’s central premise. Under German civil law, a major emitter can in principle be required to contribute to protective measures against climate-related harm in proportion to its share of emissions. Distance between the source of the emissions and the place of the damage does not, in itself, exclude liability.

On the facts, the claimant failed. The court’s experts assessed the probability that a flood from the lake would reach Lliuya’s property in the coming decades as too low to justify protective measures. Reports of the judgment put the risk at around one percent over thirty years. There was no concrete danger to his house that the law required anyone to address.

The principle was accepted, and the claim was dismissed on the evidence. This combination is the clearest guide available to how climate responsibility is likely to be decided in the years ahead.

What the International Court of Justice added

Lliuya’s case concerned a company and private law. Two months after the Hamm judgment, the International Court of Justice addressed the same subject from the other end: states and international law.

The proceedings began with a request from the UN General Assembly, adopted by consensus on 29 March 2023 on the initiative of Vanuatu. The Assembly asked two questions. What obligations do states have under international law to protect the climate system from greenhouse gas emissions? And what are the legal consequences for states that, by their acts or omissions, have caused significant harm to it? On 23 July 2025, the fifteen judges answered unanimously.

An advisory opinion does not decide a dispute between parties and is not binding in the way a judgment is. It is the court’s statement of what the law already is. On that basis, the court found that states’ obligations arise not only from the UN Framework Convention on Climate Change, the Kyoto Protocol and the Paris Agreement, but also from customary international law — including the duty to prevent significant harm to the environment and the duty to cooperate — and from international human rights law. It rejected the argument, advanced by several major emitting states, that the climate treaties form a self-contained regime that displaces those other obligations.

The court described limiting warming to 1.5°C above pre-industrial levels as the primary temperature goal under the Paris Agreement (paragraph 224). It held that states’ discretion in preparing their national climate plans is limited, and that they must act with stringent due diligence. It found that states outside the climate treaties remain bound by equivalent customary obligations. And it stated that a failure to take appropriate action to protect the climate system, “including through fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licences or the provision of fossil fuel subsidies”, may constitute an internationally wrongful act (paragraph 427).

On consequences, the court applied the general law of state responsibility. A state responsible for a wrongful act must cease it, offer guarantees of non-repetition where circumstances require, and make full reparation. That duty is subject to the usual conditions. Among them is a sufficiently direct and certain causal link between the wrongful act and the injury. The court acknowledged that establishing that link is harder in climate cases than in cases of local pollution. It declined to say that it is impossible.

On 20 May 2026, the General Assembly adopted a resolution welcoming the opinion by 141 votes to 8, with 28 abstentions. The United States, Russia, Saudi Arabia, Iran and Israel were among the states voting against.

How national courts have used it

The opinion’s practical effect depends on national courts, and several have already relied on it.

On 28 January 2026, the District Court of The Hague gave judgment in a claim brought by residents of Bonaire, a Caribbean island that forms part of the Netherlands, supported by Greenpeace Netherlands. The court found that the Dutch state had violated the residents’ right to respect for private and family life under Article 8 of the European Convention on Human Rights, and that it had discriminated against them under Article 14: adaptation planning for Bonaire had come “later and less systematically” than for the European part of the country, although the island was more exposed. The court ordered the state to set binding emissions targets within eighteen months and to produce an adaptation plan for Bonaire capable of implementation by 2030. It drew on the ICJ’s reasoning on due diligence. The judgment is open to appeal. It awarded no damages.

On 25 June 2026, the Judicial Court of Paris held in Notre Affaire à Tous and Others v. TotalEnergies that the company’s vigilance plan under French law was incomplete, because it did not adequately address emissions from the use of the products it sells. The court relied in part on the ICJ opinion. TotalEnergies has appealed.

The Federal Court of Canada referred to the opinion in 2025, noting its connection between climate obligations and the customary duty to prevent significant harm.

In each case, the remedy was an order about the future. None required anyone to compensate a past loss.

The distinctions that decide cases

Public discussion of these decisions often treats “responsibility” as a single question. In court, it is several, and a claim must succeed on each.

The first is scientific attribution: whether, and by how much, human-caused warming made a given event more likely or more severe. Attribution science can now provide such estimates for many heatwaves, floods and droughts. It is evidence. It is not a legal finding.

The second is legal causation: whether the conduct of this defendant caused this harm to the standard the court applies. In Lliuya’s case the court was prepared, in principle, to treat a fractional share of global emissions as a legally relevant cause. It was not satisfied that the harm was sufficiently likely to occur.

The third is wrongfulness. Causing harm is not in itself a breach. The ICJ defined obligations. Whether a particular state’s policy breached them is a question of fact for each case.

The fourth and fifth are standing and jurisdiction: who may bring the claim, and before which court. Only states may be parties before the ICJ, and only with their consent to its jurisdiction. In Verein KlimaSeniorinnen Schweiz v. Switzerland (April 2024), the European Court of Human Rights accepted a claim by an association while rejecting the individual applicants’ claims to be victims. National rules on standing differ widely.

The last two are remedy and compensation. A court that finds a breach may order a state or a company to act without ordering it to pay. Every climate case decided so far on the basis of the ICJ opinion has taken that route.

The question that remains open

The law has moved further in three years than in the previous thirty. States’ obligations have been authoritatively defined. The principle that an emitter may answer for its share of harm has been accepted by at least one appellate court in Europe. Courts in the Netherlands, France and Canada have applied the ICJ’s reasoning.

What no court has yet decided is how to connect a share of global emissions to a specific injury in a way that satisfies the requirement of a direct and certain causal link. The Hamm court came closest, and ruled for the defendant on the facts. The next claimant will have to show what Lliuya could not: that the harm is not only attributable to warming, but likely enough, and close enough to the defendant’s conduct, for the law to require payment. Whether any court will accept that showing is the question on which the future of climate compensation now depends.

Sources. Oberlandesgericht Hamm, Lliuya v. RWE AG, judgment of 28 May 2025 · ICJ, Obligations of States in respect of Climate Change, Advisory Opinion of 23 July 2025, paras. 224, 427 · UNGA Res. 77/276 (29 March 2023) · UN News, 20 May 2026 · District Court of The Hague, Bonaire judgment, 28 January 2026 · Tribunal judiciaire de Paris, Notre Affaire à Tous v. TotalEnergies, 25 June 2026 · ECtHR [GC], Verein KlimaSeniorinnen Schweiz v. Switzerland, 9 April 2024 · Cornerstone Barristers analysis of domestic use of the opinion (July 2026).