Ordering Paradigms in International Investment Law: Bilateralism—Multilateralism—Multilateralization

This chapter first examines the concepts of bilateralism and multilateralism, and their relevance. It then introduces the notion of multilateralization as a perspective that can overcome a schematic and static vision on ordering paradigms in international investment law (IIL). It focuses on the main source of IIL, namely international investment treaties, because these instruments are constitutive for the modern practice of IIL and investor-state arbitration. It shows how multilateral rationales play out in present-day IIL without claiming that bilateral thinking is inexistent in practice. It goes on to bridge the theoretical debate about ordering paradigms into practice and discusses how multilateral rationales play out in investment treaty arbitration, in particular in the process of interpretation of international investment agreements (IIAs), in reason-giving in arbitral decisions, and in the conceptualization of the role of arbitrators.