When customary legal systems exist alongside state regulations, individuals can choose between these different frameworks to support their claims to resources. Research suggests that such framework switching to maximize self-interest weakens and challenges resource management. Multiple legal systems are at work in India's fisheries and this study examines how they work to govern conflict over purse-seine fishing in the Sindhudurg district of Maharashtra State. Through participant observations, interviews and state fishing law reviews, this study finds evidence of strong customary legal systems, operating through local cultural practices, to protect common property rights, equitable access, ethical and ecological concerns. In contrast, state legislation appears weak because it addresses issues of local concern, such as equitable access, at a slow pace and over such a large scale as to be absent. Consequently, multiple legal systems in these fisheries do not create a management challenge that follows a predictable path towards resource degradation. Instead informal, customary rules applied alongside formal state legislation interact in complex ways that create opportunities for effective co-management.