What is the relationship between the World Trade Organization (WTO) dispute settlement mechanism and the dispute settlement mechanism under a regional trade agreement (RTA)?1 Even before the WTO was established, the North American Free Trade Agreement (NAFTA) had included a provision dealing explicitly with the relationship between its dispute settlement system and the one under the General Agreement on Tariffs and Trade (GATT), and any successor agreements. The problem is therefore not new, but only in recent years has it become more pronounced.This chapter seeks out a further approach, which looks toward the development of choice-of-law principles. We believe this is different from and potentially superior to placing an undue emphasis on the substantive value differences that define norm fragmentation, an emphasis on a jurisdictional approach, or an emphasis on both. We attempt to seek ways of managing both norm and jurisdictional fragmentation by turning away from questions about both substantive norms and jurisdictional questions. By looking at the development of choice-of-law rules (i.e., second-order norms about the selection of substantive norms), we attempt to circumvent, or at least defuse, the intense political debate that has taken place over substantive values. Our solution proposes a common set of choice-of-law rules that could be applied by different tribunals. The idea is that such choice-of-law rules – which invite formal, technical analysis – would lead to the application of the same substantive norms in each case in a relatively less politicized manner. This would reduce the risk of different results from different tribunals, which could in turn reduce the political tension inherent in jurisdictional clashes.