This Liber Amicorum, dedicated to Judge Rudiger Wolfrum of the International Tribunal for the Law of the Sea, highlights paradigmatic changes in international law, a body of law which moved during the 20th century from a law of coexistence to one of cooperation and which is now about to reflect notions of solidarity going even beyond cooperative undertakings. This leitmotif of Rudiger Wolfrum’s academic research and judgeship is represented in a comprehensive collection of essays by eminent scholars and practitioners of international law covering specific aspects of international law, including law of the sea, human rights, international environmental law, international dispute settlement, peace and security, global governance and domestic law. With its multifaceted and comprehensive overview of the evolution of international law in recent years and detailed study of current challenges this collection is a unique source of insight for all those interested in this fascinating field of law.