Sources of International Investment Law: Multilateralization, Arbitral Precedent, Comparativism, Soft Law

This chapter discusses the use of sources of international law in the settlement of disputes arising under bilateral, regional, multilateral investment treaties and investment chapters in free trade agreements, focusing specifically on particularities this field of international law displays in comparison to general international law. It first addresses the importance of bilateral treaties in international investment law and shows that their bilateral form is not opposed to the emergence of a genuinely multilateral regime that behaves as if it was based on multilateral sources. The chapter then considers the pre-eminent importance arbitral decisions assume in determining and developing the content of rights and obligations in the field. Next, the chapter looks at the increasing influence of comparative law and the influence of soft law instruments. It argues that the specific sources mix in international investment law is chiefly connected to the existence of compulsory dispute settlement through investment treaty arbitration and the sociological composition of those active in the field.