Advisory Opinion on the Obligation of States in Respect of Climate Change: Most Important Decision of the Year at the GAR Awards 2026

Gaillard Banifatemi Shelbaya Disputes is proud to have represented the Oriental Republic of Uruguay in the proceedings before the International Court of Justice that resulted in the Advisory Opinion on the Obligation of States in Respect of Climate Change, which was recognized as the Most Important Decision of the Year at the GAR Awards 2026 during Paris Arbitration Week.

Adopted unanimously on 23 July 2025, the Advisory Opinion has been widely regarded as a landmark development in public international law. The Court confirmed that States’ climate-related obligations arise under both treaty law and customary international law, and that their breach may entail State responsibility.

In the proceedings before the Court, Yas Banifatemi, Yael Ribco Borman and María del Pilar Álvarez advised and represented the Oriental Republic of Uruguay through written pleadings and oral submissions.

Following hearings involving more than 100 States and international organizations, the Court articulated a series of far-reaching principles. It held, among other things, that customary international law imposes binding obligations on all States to protect the climate system and other parts of the environment, including the duty of due diligence to prevent significant transboundary harm and the duty to cooperate in good faith. The Court also confirmed that international human rights law requires States to take the necessary measures to protect the climate system and other parts of the environment and to ensure the effective enjoyment of human rights. The Opinion further makes clear that these obligations are erga omnes, such that any State may invoke responsibility for their breach. It also confirms that breaches of climate-related obligations under treaty or customary international law may give rise to the full range of consequences under the law of State responsibility, including cessation, guarantees of non-repetition, and full reparation.

Since its pronouncement, the significance of the Opinion continues to unfold across legal and institutional settings. It is already being relied upon in domestic litigation, including by The Hague District Court in a recent decision concerning the Netherlands’ obligations relating to climate change and human rights, which illustrates the Opinion’s legal authority. The Opinion is also contributing to discussions within the arbitration community, particularly as regards the interpretation of investment protection standards in light of States’ climate-related obligations. More broadly, the Opinion is informing ongoing international discussions on the implementation of climate obligations, including within the United Nations framework.

Gaillard Banifatemi Shelbaya Disputes is honoured to have represented the Oriental Republic of Uruguay in these historic proceedings and remains committed to actively contributing to the evolving legal landscape concerning climate change.

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