This paper examines the formation and evolution of customary international law in the field of foreign investment (Parts II and III) and its various forms interaction with international treaties, focussing mainly on BITs (Parts IV to IX). Although a comprehensive study on the customary rules for...

Rules of customary international law provide basic legal protections to foreign investors doing business abroad. These rules remain of fundamental importance today despite the growing number of investment treaties containing substantive investment protection. In this book, Patrick Dumberry...

This chapter zeroes in on customary international law and examines the role played by this specific source of law in the development of international investment law. After a few considerations on the early phase of development of an international investment protection regime and the search for a...

International custom is one of the main sources of international law. As a relatively new branch of international law, international investment treaties, emerging in the late 1950s and having been very energetic since the mid-1990s, have become a driving force and an important forum for the...

The question of the existence of legal protection for foreign investors under customary international law (or “custom”) has always been controversial. As a result of this perceived lack of established customary principles, States concluded thousands of bilateral investment treaties in the...