This is the first comprehensive book that explores the subject of federalism from the perspective of comparative constitutional law, whilst simultaneously placing a strong emphasis on how federal systems work in practice. This focus is reflected in the book's two most innovative elements. First, it analyses from a comparative point of view how government levels exercise their powers and interact in several highly topical policy areas like social welfare, environmental protection or migrant integration. Second, the book incorporates case law boxes discussing seminal judgments from federal systems worldwide and thus demonstrates the practical impact of constitutional jurisprudence on policymakers and citizens alike. "This is simply the best analysis of contemporary federalism currently available. It is comprehensive in its coverage, thorough in its analysis, and persuasive in its conclusions. Every student of federalism, from novice to expert, will find benefit from this volume." Professor G Alan Tarr, Rutgers University "Wading through the thicket of the multiple forms that the federal idea has taken in the contemporary world, this remarkably comprehensive treatise backed by case law fills a long-awaited gap in the literature on comparative federalism. It combines a mastery of the literature on federal theory with a critical understanding of how it plays out in practice. Outstanding in the breadth of its scope, this magisterial survey will serve as a work of reference for generations of scholars who seek to understand how federalism works in developed as well as developing countries.