Sources of international investment law: Sonderweg or lodestar in international dispute settlement?

Abstract

This chapter discusses the use of sources of international law in the settlement of disputes arising under bilateral, regional and multilateral investment treaties and investment chapters in free trade agreements. It focuses specifically on particularities this field of international law displays in comparison to general international law and assesses to which extent these specificities are a Sonderweg of international investment law that has little relevance outside the field, or whether investment law can serve as a loadstar for how the use and relative importance of sources of international law more generally may change also elsewhere is the focus of the present chapter. The chapter addresses, first, 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 of international investment governance. Second, the chapter discusses the preeminent importance arbitral decisions assume in determining and developing the content of international investment law. Third, the chapter addresses the increasing influence of comparative law in investment arbitration and its impact on its understanding of sources. Fourth, the chapter discusses how soft law instruments influence international investment law, even though they are not binding law. The chapter argues that the particular 'sources-mix' in international investment law is chiefly a product of the existence of compulsory dispute settlement through investment treaty arbitration and the sociological composition of the field. International investment law may therefore serve as an indicator of how the sources of international law may evolve also in other international legal regimes in the presence of standard recourses to binding dispute settlement.