Where does the law and political power of any given territory come from? Until recently it was believed that it came from a single and hierarchical source of constitutional authority, a sovereign people and their constitution. However, how can this model account for the new Europe? Where state constitutions and the European Constitution, which are ultimately equally self-standing sources of constitutional authority, overlap heterarchically over a shared piece of territory. Constitutional pluralism is a new branch within constitutional thought that argues sovereignty is no longer the accurate and normatively superior constitutional foundation. It instead replaces this thought with its own foundation. It emerged on the basis of contributions by the leading EU constitutionalists and has now become the most dominant branch of European constitutional thought. Its claims have also overstepped the European context, suggesting that it offers historic advantages for further development of the idea of constitutionalism and world order as such. This book offers the first overarching examination of constitutional pluralism.Comprehensively mapping out the leading contributions to date and solving the complicated labyrinth they currently form, Klemen Jaklic offers a complete assessment against existing and new criticisms while elaborating his own original vision. Constitutional pluralism thus refined has the potential to rightfully be considered the superior new approach within constitutional thought.