This chapter re-examines the concept of territorialization to provide a framework for the anthropological analysis of the new phenomenon of transborder access to and appropriation of marine resources. The authors expand the subject of territorialization from land-based forestry to the control of people and their relations to marine resources, and reexamine the concept by addressing the everyday dynamics of the social, economic and political interactions taking place at multiple individual and institutional scales between central, provincial and district government agencies, trade networks, and resource appropriators. They also discuss two case studies involving transborder fisheries in Southeast Asia (Malaysia--Indonesia) and Australia (Indonesia--Australia), and compare them with transborder appropriation and exploitation of fisheries and other marine resources elsewhere.