World court: states have climate obligations under international law

Experts at Pinsent Masons said the ICJ’s opinion on the obligations of states in respect of climate change (140-page / 1.1MB PDF), though non-binding, could be given legal effect by national courts with enforcement powers and that this in turn could result in governments around the world applying regulatory and policy levers to drive more and faster climate-related action from businesses.

According to the ICJ, countries have an obligation under international law to ensure the protection of the environment from greenhouse gas emissions. This is imposed in two ways, it unanimously considered: first, by climate-focused international treaties, like the Paris Agreement, though this is only relevant to signatories of any such treaties, and second, by customary international law, which imposes a duty on all states to prevent significant environmental harm and prevent those in their jurisdiction from causing such harm.

Jacqueline Harris of Pinsent Masons said: “The impact is significant, with the most immediate being that states can now bring claims against each other to the ICJ for compensation. The opinion itself is advisory, meaning it is non-binding. Practically, this means that the opinion cannot be enforced against states. However, the opinion will undoubtedly still be referred to and relied on to support claims before courts which do have enforcement powers, the most obvious example being a state’s national courts.”

Katie Hancock, also of Pinsent Masons, said: “Although countries can now sue each other for climate-related harms, significant barriers still exist to successfully attributing states’ contributions to emissions – if a state’s contribution can’t be established, you can’t establish causation, and the whole action will fall. Difficulties attributing harm to countries and, indeed, companies is an issue across climate-related actions. However, the ICJ recognised that it was not impossible to establish a causal link in such cases. Campaigners believe these hurdles will be lessened as climate knowledge advances, and with the use of artificial intelligence to accelerate data analysis.”

Harris added: “As climate science and practice evolves, the courts’ interpretation of the law is evolving in response.”

Harris and Hancock said businesses are unlikely to see any immediate impact from the ICJ’s opinion, but that it could have a significant knock-on effect on their operations in time.

Harris said: “The opinion of the ICJ is that states are responsible under international law for the climate impact of the private sector in their jurisdiction. However, the opinion is advisory and does not bind national courts. That said, it can still be persuasive in how those courts will interpret domestic law.”

“What is most significant to companies is individual states’ reaction to the opinion. Its practical impact in this sense is to apply political pressure on states to impose stricter policies which more aggressively address climate change. For example, the ICJ confirmed that policies subsidising fossil fuels or approving new gas licences could breach a state’s climate obligations,” she said.

Hancock said the new opinion therefore leaves states with decisions to make.

“One obvious course which states may consider in light of the opinion is whether to implement their nationally determined contributions – the five-yearly action plans signatories to the Paris Agreement are required to draw up for cutting greenhouse gas emissions in their jurisdictions – into national regulation and policy,” Hancock said. “If done, this could drive private sector incentives and disincentives.”

“The question then for states is will they comply and alter climate policies accordingly, or will they take the position that their policies already address their duty to protect the environment from greenhouse gases? Ultimately, while businesses are unlikely to see any immediate impact from this opinion, it is significant and they should stay abreast of the international reaction to it for indications on what its real-world impact might be, especially in countries in which they operate,” she added.

Climate and sustainability adviser Michael Watson of Pinsent Masons has previously highlighted the challenges and opportunities for business leaders in being a climate leader and has advocated for climate ‘fundamentals’ to guide business’ action on net zero amidst a turbulent economic and political environment. Watson described the ICJ’s opinion as “significant” and said it should spur businesses into action.

“This significant opinion needs to be considered alongside the increasing sophistication of climate litigation generally, the role of attribution science in objectively allocating liability on corporates engaged in current and historic emissions, and the increasing pressure on governments to accelerate their policy interventions,” Watson said. “In that light, it is critical that businesses fully incorporate these factors into their strategy. This is most effectively done through effective business-relevant scenario planning and transition planning.”

Thom Wetzer, associate professor of law and finance at the University of Oxford and director of the Oxford sustainable law programme, agreed.

“This advisory opinion is in line with what has been a secular trend in climate litigation towards higher levels of state and corporate accountability,” said Wetzer. “In this opinion, the International Court of Justice confirmed that 1.5C is the legally binding temperature target under the Paris Agreement and international law. This calls for urgent action, and the court explicitly noted that states are also responsible for the actions of the private sector. As a result, we should expect renewed legal pressure on states to regulate corporate activities that contribute to climate change. Recognising that trend and the implications for business models is a key part of prudent risk management.”

The ICJ was asked to produce its advisory opinion by the UN following an initial application from Vanuatu and lobbying by students from the Pacific islands. António Guterres, secretary general of the UN, declared the opinion “a victory for our planet, for climate justice and for the power of young people to make a difference”.

The ICJ’s intervention is the latest by a court amidst increasing focus on states’ climate-related obligations by international courts.

Earlier this month, the Inter-American Court of Human Rights issued its own advisory opinion, which concluded that there is an ongoing climate emergency and that states have obligations to address this emergency under the American Convention of Human Rights.

Last year, the European Court of Human Rights held that the rights individuals enjoy under article 8 of the European Convention on Human Rights – which guarantees the right to respect for private and family life – extend to a right to be effectively protected by states against the serious adverse effects of climate change on lives, health, wellbeing and quality of life. While it did not rule definitively on the point, the human rights court further suggested that individuals’ right to life, provided for under article 2 of the Convention, could also be engaged by shortcomings in state action to address climate change.

The African Court of Human and Peoples’ Rights is also in the process of preparing an advisory opinion on climate change. 

Climate litigation generally is growing in maturity and breadth. This was confirmed in the latest edition of an annual report issued by the Grantham Research Institute, published recently. According to the report, between 2015 and 2024, 276 climate-related cases reached apex courts – such as supreme and constitutional courts – globally. More than 80% of these cases were against government defendants, though the data in the report highlighted that actions against private actors had a greater level of success.

The Grantham Research Institute report identified that at least 226 new climate cases were filed globally last year. Of these, around 20% were targeted at corporates or their directors and not just in those industries most commonly associated with climate litigation. Climate activists are taking aim at a host of sectors – including, for example, agriculture, food and textiles, retail, travel and leisure, and professional services – over their alleged role in facilitating emissions and contributions to climate-related harm.

According to an academic publication published by Wetzer and colleagues in the Science journal, these cases are increasingly central to understanding risk allocation in the context of climate change. “Legal actions determine the allocation and magnitude of climate-related financial risk exposures,” according to the study.