Despite the commons being a long-standing site of conflict, the role of social movements in common-pool resource management has been underaddressed. By exploring the role of environmental justice organizing in the San Joaquin Valley during California’s landmark groundwater reform process as a commoning practice, this article seeks to fill this gap and advance our understanding of how collective action can, and is, being leveraged to advance just and sustainable transitions. I argue that through three principal strategies of challenging participation, scope, and authority, the movement has played a formative role in a landscape of intensive enclosure. Applying a commoning lens to the case highlights the important role of not only social movements in commons management but also of commons management as a venue for the rearticulation of regional socionatural relations. Such opportunities are particularly important in underinstitutionalized rural areas where opportunities to renegotiate these relations are often few and far between. Understanding the emergence and growth of commoning communities engaged in such efforts provides several important lessons. Individual commoning strategies can help identifying principal constraints and opportunities to transcend them. To be fully understood, however, they need to be considered collectively as well as in context. In doing so, the critical importance of focusing on the work commons do, rather than produce, becomes apparent. Commoning is both a tool and a goal in itself.