The classical categories of the theory of the State used to legally understand federal systems retain heuristic value for interest to describe the various normative logics that underlie the State structure and the most integrated supra-State organizations, as long as the mechanisms resulting from processes of territorial recomposition are not discarded as anomalies. These dynamics lead one to distinguish, in these categories, between nation States and plurinational States. On the one hand, several states facing demands from sub-State national groups have inserted mechanisms in their constitutional laws that echo their plurinational nature. On the other hand, the concept of “Plurinational Federation” seems to be the most appropriate to grasp the legal nature of the European Union.