Unilateralism in international law: implications of the inclusion of emissions from aviation in the EU ETS

The 1997 Kyoto Protocol deferred negotiations on emissions from aviation to the International Civil Aviation Organization (ICAO).[1] Also within this specialised body, agreement on how to deal with emissions from aviation has been difficult to reach.[2] Frustrated by the lack of progress, the European Union (EU) decided to act unilaterally to reduce emission from aviation, by including aviation within its Emission Trading System (ETS). Initially, the EU set out to include in the ETS emissions from all major aircraft flying to or from European airports, even when these fly over the high seas or foreign territory.[3] Many States, however, viewed the EU’s initiative as a unilateral act in violation of their sovereignty. The EU has since suspended the application of the ETS to foreign aircraft.[4] Even so, this incident raises important questions concerning the legality of unilateral acts under international law. This note considers when and how a State or a regional organisation may legitimately take unilateral measures to protect the environment. The note will not consider the legality of including foreign aircraft within the ETS, which has been dealt with elsewhere.[5] Instead, it will focus on the legality and importance of unilateral acts for the development of international law.