ICJ declares legal duty on climate action

The Court determined that the 1.5 °C temperature target under the Paris Agreement is legally binding and that customary international law imposes binding obligations on states to take preventative and precautionary measures to avoid climate harm, including through the regulation of private actors. The opinion arrives two years after the United Nations General Assembly (UNGA) adopted resolution 77/246 requesting the advisory opinion, and six years after a group of students from the University of the South Pacific began campaigning on this issue. 

The court also rejected arguments posed by high-emitting states that climate treaties are lex specialis and render other rules of international law inapplicable. It found that multiple sources of law – such as climate change treaties, customary international law, international human rights law, and principles – impose legal duties on states to prevent "transboundary environmental harm", take due diligence measures to reduce greenhouse gas (GHG) emissions, act with precaution, and adapt to the adverse impacts of climate change. 

While ICJ advisory opinions are not legally binding, they serve as highly authoritative guidance and are expected to influence both domestic and international climate litigation. This particular opinion is especially notable due to unprecedented engagement: 91 written statements and 62 written comments were submitted by states and international organisations, and 96 states and 11 organisations made oral submissions.

Key findings 

In its 140-page advisory opinion, the Court left no doubt that international law provides a sufficiently robust framework to assess climate-related state responsibility. Based on the framework identified by the Court, the ICJ derived concrete obligations for states. 

Key findings by the Court include: 

• The primary agreed legally binding target for limiting the global average temperature increase under the Paris Agreements is 1.5 °C. Every increment of global warming escalates climate risk.
• States’ discretion in preparing Nationally Determined Contributions (NDCs) under the Paris Agreement is limited; parties must exercise due diligence to ensure that, collectively, NDCs align with the 1.5°C temperature goal.
• Customary international law imposes binding obligations on states to take preventive and precautionary measures to avoid climate harm, including through the regulation of private actors.
• Failure to take appropriate measures to protect the climate system from GHG emissions – including through fossil fuel production and consumption, the granting of new exploration licences, or the provision of subsidies – may constitute an internationally wrongful act attributable to the state.
• As part of their due diligence obligations states must regulate emissions by private actors within their jurisdiction or control. If they fail to do so, responsibility may arise.
• Customary international law and climate treaties, such as the Paris Agreement, both impose binding obligations on states to undertake adaptation measures in line with the best available science. Fulfilment of adaptation obligations is to be assessed against a standard of due diligence. Developed countries have an additional responsibility to help developing countries meet the costs of adaptation.
• Emissions can be attributed to individual states, including cumulative historical and current emissions, through scientific evidence. This enables states to invoke legal responsibility.
• Obligations pertaining to the protection of the climate system and other parts of the environment from anthropogenic GHG emissions, in particular the obligation to prevent significant transboundary harm under customary international law, are obligations erga omnes. As such, any state can invoke responsibility for breaches of these climate obligations – not only those directly affected. 

Legal consequences can be triggered by climate inaction 

Violating these obligations can trigger responsibility under international law, including cessation, assurances of non-repetition, and reparation. The latter may amount to restitution such as ecosystem restoration or rebuilding climate-resilient infrastructure, compensation for financially quantifiable loss, or satisfaction including a public acknowledgement or apology. 

Responsibility is determined on a case-by-case basis based on a "sufficiently direct and certain causal nexus" between the wrongful act and the harm suffered. 

Even where a state has breached its obligations, it has a continuing obligation to comply. In example, they must continue to submit new or revised NDCs under the Paris Agreement that must be progressive and ambitious. 

A potential blow to the fossil fuel industry

The advisory opinion may have significant implications for energy producers, as the Court clarified that the "relevant conduct" for the proceedings was not limited to actions that directly result in GHG emissions, such as fossil fuel combustion. Instead, it comprises "all actions or omissions of states which result in the climate system and other parts of the environment being adversely affected by anthropogenic emissions". Fossil fuel production is therefore included in the scope of conduct that may be in breach of international law. 

Issuing fossil fuel exploration licences, allowing new production projects, or granting fossil fuel subsidies can be a breach of international law. Specifically, the Court stated that: 

"[A] state’s failure to take appropriate action to protect the climate system from GHG emissions – including through fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licenses or the provision of fossil fuel subsidies – may constitute an internationally wrongful act".

Several judges also issued separate declarations regarding their interpretations of the case. Judges Bhandari and Cleveland, in a joint declaration, emphasised that staying below 1.5 °C means no new fossil fuel projects may be developed. Environmental impact assessments (EIAs) for new projects must include downstream (“Scope 3”) emissions, in line with the EFTA Court’s advisory opinion (referenced by the Borgarting Court of Appeal) that EIAs must cover emissions from the combustion of extracted petroleum or natural gas.

Citing the EFTA Court, the judges stated that the authorities assessing the project "are in full control of whether or not the environmental effects will occur".

Looking ahead

The ICJ advisory opinion may provide additional leverage for claimants in ongoing litigation. In Norway, the Borgarting Court of Appeal will this autumn hear a case on whether the state must assess downstream (Scope 3) emissions in EIAs for new oil and gas licences.

A question that remains is how this advisory opinion will shape future policies in fossil fuel-producing countries such as Norway. This will be a matter of considerable interest in the years to come. 

Amid a global increase in climate-related litigation, the ICJ has delivered a clear message: legal systems must address climate obligations, and further delay is no longer acceptable. As such, the advisory opinion serves as an important new tool in court-driven efforts to address climate change.