This coauthored treatise on a “constitutional theory for [sic] a democratic European Union” appears as the international debate about global constitutionalism is flourishing in an increasingly interdisciplinary field. This field can be roughly distinguished according to functionalist, normative, and pluralist perspectives that motivate research on constitutionalization “beyond the state” or “unbound from” the state, that is, processes whereby constitutional principles, norms, and rules are either transferred from the context of modern nation-states into the global realm or brought to the fore “outside” of modern constitutional reach. Two theoretical standpoints are notably distinguishable: On the one hand, modernists seek to rebind constitutional norms either in the nation-state or within a global constitution (compare, e.g., the respective work of Martin Loughlin and Dieter Grimm for the former and Bardo Fassbender, Jürgen Habermas, or Jean Cohen for the latter). On the other hand, late modernists are engaged in rethinking the validity of modern constitutional norms in the twenty-first century (compare, e.g., the respective contributions by James Tully, Neil Walker, and Rainer Forst).

The book's subtitle phrase of promoting a constitutional theory “for” the European Union, the substantive reference to “traditional constitutional theory made in the image of European nation-states” (p. 191), and the central argument about working with the synthesis of constitutional theory of the EU's member states, which places the “regulatory ideal” of modern constitutionalism squarely at the center of this book's approach, sustain the authors' preference for the modernist perspective. They write that “key components of the theory are the regulative ideal of a common constitutional law, of a constitution made up of the collective of national constitutions, and the understanding that normative synthesis can go hand in hand with, and even be facilitated by, a pluralistic institutional structure” (p. 15). Defined thus, the proposed “theory of constitutional synthesis” tries to—and, as the authors claim, actually does—make sense of the EU's constitutional development (p. 213).

While this approach echoes the sui generis argument about the EU's political form that has long accompanied European integration theory proper, John Erik Fossum and Agustin José Menéndez draw heavily on the “regulatory ideas” of modern constitutionalism. The goal of the “synthetic” constitutional project thus sits quite comfortably with federalist visions of European idealists in the prestage of European integration theorizing. It is notable that by presenting and “testing” the relevance of their theory of constitutional synthesis, the authors manage with little reference to the emerging interdisciplinary field of global constitutionalism. Instead, the book refers almost in passing to a somewhat random selection of Europeanists whose suggestions are all ultimately dismissed (among them Ingolf Pernice, Christian Joerges, Wolfgang Wessels, Joseph Weiler, and Andrew Moravcsik, discussed in no more than a page each [pp. 69–75]).

What then, does the theory do for the range of constitutional issues that are at stake in Europe and elsewhere, as constitutionalization moves into previously nonconstitutionalized territory?

For the ambitious goal of promoting a concise theory, it is notable that the authors use this theory of constitutional synthesis both for comparative and for normative purposes. That is, the theory of constitutional synthesis is considered synonymous with the actual practice of constitutionalization (defined as a “social practice,” with a nod to Ronald Dworkin). As the authors explain, “[C]onstitutional synthesis proceeds by transferring the collective of national constitutions to the European constitution” (p. 92). This theoretical cum practical development is demonstrated throughout the book.

After developing the theory in Chapters 1 and 2 and then applying it to the reconstruction of constitution making in the European Union in Chapters 3 and 4, the authors apply the theory to “untangle” the “Gordian knots of European constitutional practice” in Chapter 5 (p. 168). (Here, the “theory of constitutional synthesis offers solutions to … two riddles [of genesis and primacy]. It provides a distinct yet coherent conception of the Union's constitutional vocation [sic] and a key to the analysis of the Union's institutional and constitutional features” [ibid.].) The “genesis riddle” is solved, for “constitutional origin is no longer a mystery when we consider the role that national constitutions played in enabling the ‘synthetic’ constitutional moment and in defining the constitutional ground on which European constitutional law was built” (ibid.). In turn, “[C]onstitutional synthesis claims that the primacy riddle is dissolved once we take into account that European constitutional law and national constitutional law cannot be properly portrayed as two sets of differentiated constitutional norms” (p. 171). The authors then move on to “test” the theory's relevance beyond Europe by turning to the case of constitution making in Canada in Chapter 6. Chapter 7 summarizes lessons for the future.

In sum, the relevance of the theory is demonstrated by applying it to the case of the EU and the process in which member states' respective constitutional law was bundled together, on the one hand, and to the theoretical analysis and evaluation of this process as well as the Canadian case, on the other (p. 203). (Thus, the book explores “Canadian synthetic lessons for Europe”). Subsequently, “synthetic theory” entails a “synthetic approach,” which, as the authors claim, “discerned the synthetic character of the Canadian constitutional experience” (p. 215). Given that the synthetic approach is applied to theory and practice alike (e.g., “Canada did not abandon the synthetic path through patriation”; p. 215), the value-added for other than normative analysis remains to be shown (i.e., in applying a synthetic theory to identify synthetic constitutionalism, the finding that synthetic constitutionalization is actually happening should not come as a surprise). One wonders what this theory would have to say about other than “synthetic” constitutional practice. To begin with, British academics in particular will frown at the definition of “the formal constitution” as “necessarily a single, written, and socially recognised constitution” (p. 20).

This said, this narrative told by two connoisseurs of constitutionalism offers an insightful read, especially for those interested in the historical background of the “long constitutional season” in Europe (p. 15), encompassing the Laeken and Lisbon Treaty negotiations and the long lead up to the “synthetic constitutional moment” over the five decades from the Treaty of Paris to the Treaty of Nice (p. 15).