Dominik J. Snjka undertakes an exploratory journey in search of an international law of spatial planning in this study distinguishing between two conceivable functions of international law. On the one hand, this forms the legal framework of sovereign spatial planning and, on the other, it can itself become an instrument of sovereign planning. After looking at structural preliminary considerations, the author takes stock of international environmental regulation requirements for spatial planning, which are then reflected in international maritime law. In the last part, existing approaches to spatial planning through international law are examined, covering trans-boundary infrastructures and protected areas as well as spatial planning by international organizations.