The resolution of conflicting claims to land has long stood at the heart of the project of international law. Indeed, the encounter between the order envisaged by advocates of the law of nations and what Georges Scelle called the “obsession with territory” has been a defining struggle for our field, demonstrating to some its promise and to others its futility. Much, perhaps even most, legal scholarship on this subject over the last century has focused on adjudication by ad hoc tribunals or standing courts, in which jurists have derived and invoked hallowed principles that enabled them to draw lines—across mountains, deserts, rivers, and human settlements—where mere politicians had never succeeded. The doctrines on territorial sovereignty emanating from these decisions suggested a bright future for law. Yet a more pessimistic appraisal would see a darker image, one characterized by war—interstate, colonial, and civil—and territorial settlement whose lines have reflected power and politics, but surely not norms. Adjudications could be viewed as a sideshow for addressing small-scale conflicts, the results dictated more by a desire to appease both parties than by reasoning toward some principled solution.