This book examines the challenges posed to contemporary international law by the shifting role of the border, which has recently re-emerged as a central issue in international relations. It posits that borders do not merely correspond to States’ boundaries: indeed, while remaining a fundamental tool for asserting States’ power, they are in fact a collection of constantly changing spatial limits. Consequently, the book approaches borders as context-specific limits and revisits notions traditionally linked to them (jurisdiction, sovereignty, responsibility, individual rights), while also adopting the innovative approach of viewing borders as phenomena of both closedness and openness. Accordingly, the first part of the book addresses what happ...