In the debates about whether to take constitutionalism beyond the state, the European Union invariably looms large. One element, in particular, that invites scholars to grapple with the analogy between the European Union and global governance is the idea of legal pluralism. Just as the European legal order is based on competing claims of ultimate legal authority among the European Union and its Member States, so, too, the global legal order, to the extent we can speak of one, lacks a singular, uncontested hierarchy among its various parts. Scholars have accordingly begun to consider pluralism within the European Union as a model from which to glean more general principles that may be applicable to pluralism and constitutionalism elsewhere. If we can find constitutionalism within the pluralist system of the European Union, so the argument goes, perhaps we can find constitutionalism within the international legal system as well.This paper takes a fresh look at constitutionalism and pluralism by bringing heterarchy home. In so doing, it explores a comparison that has been uniformly overlooked in the scholarly literature. This chapter examines the similarities between the pluralism that lies at the core of European constitutionalism and aspects of pluralism in U.S. constitutional practice. With regard to these two systems, the chapter makes three claims. First, in both systems important questions of final legal authority remain essentially unsettled. Second, in both systems, this absence of hierarchy of legal authority does not lead to chaos, but constitutes a system of order. Third, the management of constitutional conflict and the resulting accommodation turn on what I claim are the three primary values of constitutionalism: voice, expertise, and rights. Reaching beyond these two systems, the comparative inquiry pursued here helps answer what may be the most pressing question for those who seek to understand global governance in the language of constitutionalism. The comparison reveals that constitutionalism does not depend on traditional hierarchy among systems or interpretive institutions. Instead, constitutionalism can be realized within a system of heterarchy. Constitutionalism stands for a project of governance in which actors endeavor to realize the primary values of voice, expertise, and rights. And it is these three values that the idea of constitutionalism, if taken seriously, aims to vindicate at the level of global governance as well
