This publication deals with the confluence of two increasingly important aspects of constitutional law at the turn of the twenty-first century: constitutional justice, without which the constitution might be regarded as lex imperfecta; and federalism and regionalism in a world where the unitary state is less and less the norm. In federal and regional states, just as in other states which comprise entities with legislative powers (autonomous areas), the Constitutional Court must guarantee peaceful resolution of disagreements between the central state and those bodies. This book presents a variety of solutions introduced in around fifteen European and Northern American states, taking into account their diversity both historically and in their day to day practice.