ICJ Advisory Opinion: State Responsibility in the Climate Crisis under International Law

In its landmark advisory opinion on Question B, the International Court of Justice (ICJ) has clarified the legal consequences for states that fail to meet their climate obligations. The opinion offers significant legal insights into attribution, causation, and the scope of state responsibility under international law in the context of climate change.

The Court rejected the notion that the Paris Agreement or other climate treaties constitute a self-contained legal regime. It affirmed instead that the general rules of state responsibility under customary international law continue to apply. There is no legal conflict between the UN climate framework and broader international legal norms; rather, the two are complementary and mutually reinforcing.

On the matter of attribution, the ICJ confirmed that the acts or omissions of any state organ—whether executive, legislative, or judicial—are attributable to the state itself. Importantly, the Court emphasized that failure to act can constitute a breach of legal obligations. This includes the failure to regulate private sector emissions, the continuation of fossil fuel subsidies, or the absence of adequate legislative measures. The breach lies not in greenhouse gas emissions per se, but in a state’s failure to exercise due diligence to protect the climate system.

Addressing the question of causation, the ICJ acknowledged the inherent challenges in linking specific state actions to climate harm. However, it reaffirmed that existing international legal standards are sufficiently flexible to accommodate the cumulative and transboundary nature of climate impacts. The required standard of causation—namely, whether the harm is “sufficiently direct and certain”—remains applicable. The Court outlined a two-step approach: first, determining whether a climatic event is attributable to anthropogenic climate change through general scientific assessments; and second, legally assessing the extent to which the damage can be linked to the conduct of one or more states. The involvement of multiple states in contributing to climate change does not exempt individual states from legal responsibility. Each injured state retains the right to invoke the responsibility of one or several states that have failed to meet their obligations.

The ICJ also affirmed that climate protection obligations hold both erga omnes and erga omnes partes status. The obligation to protect the climate system is owed to the international community as a whole, while treaty-based obligations, such as those under the Paris Agreement, are owed collectively among the parties. This means that all states party to such agreements have a legal interest in the compliance of others, particularly with respect to core commitments like emissions reductions.

As for the legal consequences of breaching climate obligations, the Court stated that responsible states must cease their unlawful conduct and take effective measures to prevent its recurrence. They are also expected to provide assurances and guarantees of non-repetition. In terms of remedies, restitution—restoring the environment to its prior state—is often impractical but may include ecosystem restoration where feasible. Where restitution is not possible, states may be required to provide compensation, although the quantification of climate-related damages remains legally and scientifically complex. Additionally, states must use all available means to reduce greenhouse gas emissions effectively.

Finally, while the ICJ reaffirmed the critical role of international law in addressing the climate crisis, it also emphasized that legal mechanisms alone are insufficient. Combating climate change requires a global cooperative effort and sustained political and societal commitment.

This opinion marks a significant advancement in international climate jurisprudence, reinforcing that climate inaction can result in concrete legal consequences and establishing a clear framework for holding states accountable under international law.