Times of transition are often more exciting than those of routine and continuity, but they are typically also disorderly and confusing. Old paradigms fade, but new ones only emerge slowly, and their multiplicity leads to protracted phases of co-existence, competition and conflict. The current ‘disorder of orders’ in the conceptualization of postnational law is a signal of such a transition and an indication of its depth. The ‘Westphalian’ system, with its clear separation between domestic and international levels of law and only relatively thin forms of coordination and cooperation in the latter, has broken down under the weight of Europeanization and globalization, but its successor has not been appointed yet. Several candidates are in the race, and one main dividing line – the one this chapter focuses on – is between constitutionalist and pluralist approaches to postnational order. Both of these come in many guises, but they typically differ in their understanding of central structural traits of the legal and political order. While constitutionalists, drawing on domestic inspirations, generally strive for a common frame to define both the substantive principles of the overall order and the relations between its different parts, pluralists prefer to see the postnational realm as characterized by heterarchy, by an interaction of different suborders that is not subject to common legal rules but takes a more open, political form.
This contrast may seem overdrawn; perhaps one should steer a less conflictive path and work towards reconciling these two visions in some form of ‘constitutional pluralism’. But such a conciliatory move would conceal, rather than bring into relief, the theoretical and practical differences that exist between constitutionalist, unity-oriented and pluralist, heterarchical conceptions. Even if in the current debate some of the positions may be relatively close, highlighting the contrast between the two strands will be useful to probe more deeply into their respective foundations and into the choices we face in the conceptualization and construction of the postnational legal order.