States’ legal obligations to equitably decarbonise international aviation

Recent opinions from the ICJ, ITLOS and IACtHR confirm that states have binding obligations to reduce emissions, including from international aviation. And yet, there is still a huge gap between what is required and what is being done to tackle aviation emissions. This briefing sets out how this can be addressed at the 42nd ICAO Assembly.

Background

The aviation sector is a substantial contributor to climate change, accounting for 2.5% of global energy-related CO2 emissions in 2023, and 1.9% of total GHG emissions in 2019. In addition, the sector is also a known contributor for non-CO2 impacts, in particular contrail formations and NOx emissions.

The 42nd Assembly session of the International Civil Aviation Organization (ICAO) is being held in September 2025. This is a key opportunity for ambitious Member States and organisations to highlight any shortcomings in current efforts to reduce aviation emissions, and take the steps needed to change this.

What’s covered in the briefing?

There is a clear divergence between legal obligations and current international action on aviation emissions. This briefing highlights the evolving legal landscape of States’ binding requirements to regulate emissions, including international aviation, and covers Advisory Opinions (AO) from:

• The International Court of Justice (ICJ)

• The International Tribunal for the Law of the Sea (ITLOS)

• The Inter-American Court of Human Rights (IACtHR)

This briefing sets out policy recommendations to be addressed at the ICAO Assembly, along with the actions and key indicators to facilitate the necessary policy changes. As the specialised United Nations agency tasked with setting global standards for the international civil aviation sector, ICAO must reflect these obligations through its governance.

Read our briefing on States’ legal obligations to equitably decarbonise international aviation.