The question of which European or international institution should exercise public authority is a highly contested one. This new collection offers an innovative approach to answering this vexed question. It argues that by viewing public authority as relative, it allows for greater understanding of both its allocation and its legitimacy. Furthermore, it argues that relations between actors should reflect the comparative analysis of the legitimacy assets that each actor can bring into governance processes. Put succinctly, the volume illustrates that public authority is relative between actors and relative to specific legitimacy assets. Drawing on the expertise of leading scholars in the field, it offers a thought-provoking and rigorous analysis of the long debated question of who should do what in European and international law.