This chapter offers a new framework for theorizing about the roles of different types of actors who participate in processes of cross-fertilization. All of these actors have complex or mixed motives: while actors may place some value on the coherence of the international legal system, they weigh such systemic concerns against other, more immediate concerns. International judges, for example, may place value on the coherence of the international legal system, but they may place greater emphasis on the autonomy of their own specialized or regional legal order, on the normative values of that order and on their own authority within that order. Other actors, by contrast, may place little or no value on international legal coherence, but favor or oppose cross-fertilization as a function of its effect on the their likelihood of prevailing in a dispute. In a world of complex actor preferences, the process of cross-fertilization is likely to resemble, not a consensual process of management, but a constant struggle among a wide variety of actors, some of whom will champion cross-fertilization while others seek to prevent or limit it.

This introduction reviews scholarship on international legal fragmentation, lays out a framework for understanding international judicial cross-fertilization, and previews the contributions and their findings. Existing scholarship on international legal fragmentation, we argue, has moved through three phases over the past several decades. In the first, legal scholars and practitioners reacted with alarm to the judicial proliferation of the post–Cold War years, which they feared would create overlapping jurisdiction and conflicting interpretations of law. Following this period, the new century saw the pendulum swing toward a second, more optimistic picture in which international courts addressed fragmentation through “management” techniques, producing unity in international law. We can detect the opening salvos of a third wave, as skeptics have questioned the management account, pointing to the mixed motives of international judges and the limits of cross-fertilization. In this volume, we build on the existing literature by theorizing the actors of cross-fertilization and their motives, and by distinguishing between procedural and substantive cross-fertilization.