Sasi, the spatial and temporal closure of fields, forests, reefs and fishing grounds, is a conspicuous feature of many Moluccan societies. Despite increasing domestic and international awareness and praise of what is considered by many analysts to be an exemplary indigenous resource conservation tradition, the practice is in decline in many parts of the Thousand Island province, and in many villages has disappeared altogether. This study examines the practice of managing Trochus niloticus (Topshell) harvests in Ohoirenan, a village on the eastern coast of Kei Besar in the District of Southeast Maluku. Trochus is one of the most important sources of cash income for Kei villagers, and until recently, for the district government as well. Since 1987, trochus has been classified as a protected species in Indonesia, and regulations have been issued to regulate the cultivation, harvest and transport of this and other protected species. This article briefly introduces Kei customary law and property relations, followed by a description of sasi and its application to reef habitats and trochus harvests. Examining a territorial conflict between Ohoirenan and a neighboring village, and more recent contention arising from government efforts to protect the species, the article explores issues of society–nature and state–society relations as pertain to natural resource management in Indonesia. Sasi continues to function as an exemplary common property resource (CPR) management institution in Ohoirenan, assuring equitable distribution of the benefits deriving from controlled extraction of a local resource. But, erratic and uneven enforcement of “one-size-fits-all” centralized conservation policy and law, combined with collusion and self-interest on the part of various parties, combine to threaten both the resource and the institutions that have successfully and sustainably managed it in this region. Within the context of a centralized, state-led natural resource management system, the national species protection precludes the establishment of sensible, mutually beneficial co-management regimes that could serve the interests and employ the inherent knowledge and capabilities of local communities, traders, and government agents.