Regulating the Environmental Integrity of Carbon Offsets for Aviation: the International Civil Aviation Organization’s Additionality Rule as International Law

The International Civil Aviation Organization (ICAO) is implementing a Carbon Offset Reduction Scheme for International Aviation (CORSIA). This article applies the law of international responsibility to examine whether ICAO’s acts and decisions creating CORSIA require that ICAO ensure CORSIA’s environmental integrity and focuses on the requirement that CORSIA offsets represent additional reductions, avoidance, or removals in greenhouse gas emissions beyond what would otherwise occur. It finds ICAO created an ‘additionality rule’ for CORSIA. The article further determines that this rule should be construed as imposing an international obligation on ICAO, the violation of which could trigger ICAO’s legal responsibility. The article concludes by reflecting on potential standards for measuring ICAO’s compliance with this rule, and how classifying it as part of international law could help hold ICAO to account for CORSIA’s environmental integrity.