This chapter builds on discussions on a range of conceptual and normative issues relating to legal pluralism, customary law, environment management, and conservation. It begins by defining customary land tenure and explaining its importance to the people of the Pacific. The chapter then examines a range of legislation from a number of Pacific Islands countries pertaining to customary land. This is to show the legal basis of customary land tenure and its recognition within the formal state legal system. The chapter focuses on disaster and climate change as existential threats to Pacific communities because the islands they occupy are vulnerable to inundation and erosion due to floods and sea level rise. Such threats have devasting effects on the environment, which suggests a clear link between customary land tenure and environment conditions. In some Pacific Island countries, a system of registration of interests in land was established prior to attaining political independence from a colonial power.