Governmental powers can be apportioned vertically at different levels. Five levels of vertical government are distinguishable, moving from purely local to the truly global: (1) local, ie municipal or citywide; (2) substate-regional (3) State; (4) supranational, eg the European Union; (5) and arguably global eg the WTO and the UN. This book focuses on levels (2) (3) and (4). It intends to analyse the interaction of the constitutional and political orders of EU Member States that exhibit varying degrees of territorial pluralism, their sub-state entities and the supranational organisation to which they belong. It does so by comparing the division of competences for internal policies but also for external affairs, the various models of fiscal federalism and the different systems for the effective protection of individual and collective rights within various European multi-level constitutional orders. Following a functional method of comparative constitutional law, on which the ERC-funded European and National Constitutional law project is based, the current book provides for an important study of the application of the federal principle within the European constitutional space.