In 2015, frustrated by the slow pace of negotiations in the International Maritime Organisation, the EU issued Regulation 2015/757 on the monitoring, reporting, and verification of carbon dioxide emissions from maritime transport. Echoing the controversial Aviation Directive, the Regulation is intended to support a unilateral market-based measure, and includes emissions from outside EU territory. This raises the question whether, according to international law, the EU has jurisdiction to regulate such ‘extraterritorial’ circumstances. In exploring the appropriate jurisdictional bases, we argue that neither the Law of the Sea Convention, nor world trade law definitively decide this issue. We therefore devote more detailed attention to the customary international law of State jurisdiction supplementing these regimes. We seek to build on the existing analysis by examining climate change as a ‘common concern of mankind’. We argue that this emerging concept has distinct legal implications that can and should be accommodated within the interest-balancing exercise underlying the jurisdictional analysis.