This article explores the intersection of, and relationship between, the Biodiversity Beyond National Jurisdiction (BBNJ) Agreement and the Antarctic Treaty System (ATS). It examines the status of the Southern Ocean as an ‘area beyond national jurisdiction’ before analysing the application of the ‘not undermine’ principle to the ATS as developed in Article 5 BBNJ Agreement. The article examines the implications of the BBNJ Agreement in relation to environmental impact assessments, area-based protection, marine genetic resources and dispute resolution within the ATS. It argues that the thus far defensive approach of the Antarctic Treaty parties to the BBNJ Agreement is neither sustainable nor in the long-term interests of either agreement. It argues for positive engagement between the two regimes for the ultimate benefit of Southern Ocean governance.

This article examines reactions to the South China Sea and Chagos Marine Protection Area arbitrations under the United Nations Convention on the Law of the Sea (UNCLOS), in particular concerns about the potential widening of Part XV jurisdiction and its impact on the dispute resolution system's consent basis. It argues that assessing the impact of such cases involves a characterization of both the function of Part XV and of international judges. Ultimately, it suggests that the best test of whether UNCLOS case law has gone too far is the reaction of States in designing dispute settlement under the new Agreement under UNCLOS on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction.