The rise of multilateral investment treaties : and the development of customary international investment law

Abstract

This study focuses on multilateral investment treaties (MITs), namely investment treaties per se or free trade agreements (FTAs) with investment chapters concluded by three or more parties. The hypothesis of this study is that MITs develop customary international investment law. In fact, while MITs have had a profound impact on international investment law, their contribution is often overlooked by the volume of bilateralism, which accounts for more than 3,000 bilateral investment treaties (BITs) and bilateral FTAs, as opposed to forty MITs. Specifically, this study revolves around four main axes. First, it establishes that BITs and bilateral FTAs, taken as a whole, crystallise customary international investment law. Second, it explains that the conclusion of MITs confirms this proposition. Third, it shows that MITs are increasingly used as codifications of international investment law and as homogenising media that create and codify customary international investment law. Moreover, this study explains that the current move towards large scale MITs, such as the Trans-Pacific Partnership Agreement or the EU-Canada Comprehensive Economic and Trade Agreement, provides ample proof of international investment law’s shift from bilateralism to MITs, thus making it necessary to examine the historical roots of MITs and their distinctness from other forms of multilateralism. Fourth, this study demonstrates that the parallelism caused by the interrelation and co-existence of MITs alongside BITs and FTAs does not necessarily undermine the codifying abilities of MITs. Rather, the pervasive parallelism existent in international investment law fosters rather than hinders the codifying abilities of MITs, even if it is at times difficult to reconcile parallelism through treaty interpretation.