The Formation and Identification of Rules of Customary International Law in International Investment Law

By Patrick Dumberry, published by Cambridge University Press, December 2018

This book provides a comprehensive analysis of the phenomenon of customary international law in the field of international investment law. It analyzes two questions: how customary rules are created in this field and how they can be identified. The book examines the types of manifestation of state practice that should be considered as relevant evidence for the formation of customary rules and the extent to which they are different from those existing under general international law. It also analyzes the concept of opinio juris in investment arbitration. Available at