There has been a considerable amount of legal scholarship regarding the use of "hard" and "soft" law in international governance, written from legal positivist, normative, and political economy perspectives. Hard law generally refers to legal obligations of a formally binding nature and soft law to law that is not formally binding but may nonetheless exercise significant influence on behavior. Much of this literature assesses the relative functional attributes and deficiencies of hard and soft law techniques as alternatives for international governance. This literature also often stresses how hard and soft law can be used as complementary and evolutionary means for international problem-solving to reach desired regulatory goals.

We take a different approach. First, we begin by grounding our study in a theoretical understanding of the diverse challenges confronting regulatory cooperation in a world characterized by power asymmetries, distributive conflicts, and a fragmented international legal order. Second, we focus on how hard and soft law mechanisms interact in such different contexts. Because of the existing literature's focus on how hard and soft law mechanisms lead to cooperative outcomes, much of the existing literature can be accused of selection bias. In contrast, we address the conditions under which hard and soft law are more likely to act as complements and lead to cooperative outcomes and those where they are more likely to be used as antagonists in strategic bargaining that reflects underlying disagreements among states. We examine, in particular, how the use of hard and soft law varies and leads to different outcomes when the US and EU cooperate or compete.

This paper is in four parts. Part I provides a review of the literature on hard and soft law and their relative attributes, and how hard and soft law can act as complements. Part II provides the background theoretical context for assessing the roles and interaction of hard and soft law in international regulatory governance, as alternatives, complements and antagonists, namely the role of US and EU economic and institutional power, the role of distributive conflict between the US, EU and third countries, and the challenges posed by international regime fragmentation. Part III assess how, in the presence of distributive conflicts and fragmented regime complexes, hard and soft law can just as likely act as opposing tools aimed to counter each other's influence, focusing on the dispute over genetically modified foods as an illustrative case study. Part IV then sets forth three hypotheses regarding how hard and soft law instruments interact in international governance, and, in particular, the conditions under which they work in a complementary or opposing manner.