The phenomenon of internationalization, combined with the internal process of state fragmentation, has challenged the Westphalian model of sovereignty, replacing it with a "disaggregated sovereignty" in which transnational networks have become the primary vectors of international cooperation as well as the primary actors in international policy making. This evolution poses a multifaceted challenge to state-centered constitutionalism since the networks are capable of emancipating themselves from the latter's requirements by creating parallel sets of norms. With their growing autonomy, the networks can gradually replace state action, which raises issues of accountability and legitimacy. Effectively addressing these challenges implies a paradigm shift—from the state-centered approach to constitutionalism toward a broader vision of a constitutionalism beyond the state. At the same time this shift articulates the reflections around notions such as pluralism and polycentricity. This state of affairs requires further examination of the legitimacy of the two faces of these networks—the new model of expert governance, with efficiency maximization, as well as the new paths of solidarity and cooperation that they imply.