Foreword

This thesis was submitted as part of the requirements for the degree of Master of Laws (LL.M.) at the Faculty of Law, University of Oslo, and carries 30 ECTS credits. It is published substantially in the form in which it was submitted and examined. The only changes made since submission are the correction of a small number of grammatical and typographical errors. The thesis examines flag State responsibility for the protection of marine biodiversity in areas beyond national jurisdiction, with particular emphasis on environmental impact assessment obligations under the United Nations Convention on the Law of the Sea (‘UNCLOS’) and the Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction (‘BBNJ Agreement’). It further considers the due diligence responsibilities of flag States, including their role in determining whether reliance may be placed on a previous assessment under the BBNJ Agreement's equivalence mechanism. Situated at the interface between the law of the sea and international environmental law, the thesis examines an evolving area of public international law at a time of significant legal and institutional development. Increasing human activity continues to place growing pressure on marine ecosystems, further highlighting the importance of these issues.

I would like to express my sincere gratitude to my supervisor, Professor Alla Pozdnakova, for her encouragement and support throughout this process. Her expertise, constructive guidance, and insight have been instrumental in shaping this thesis. I would also like to thank my husband for his patience and understanding during the preparation of this thesis, and for his continued belief in me.

Bergen, July 2026

Mathilde Louise Raa Lie-Nielsen