This case study examines co-management in national parks and protected areas using theory on institutional arrangements of common pool resources. I apply a co-management framework to evaluate how characteristics of the community, of the resource, of the state agency, and of the institutional arrangement support co-management in a partnership between Parks Canada and Hul’qumi’num communities in the Gulf Islands National Park Reserve (GINPR). Results show that state and community partnerships can foster co-management even without formal structures for sharing power and decision-making. Notably, the nature of the institutional arrangement, which focuses on restoring a clam garden, supports co-management by challenging conservation approaches that restrict human activities in order to protect biodiversity. In the GINPR, informal processes were integral to successful outcomes. These processes directed energy to address local priorities using conservation approaches that are driven by local First Nations values. Nevertheless, co-management is limited without equitable sharing of power in key management functions: planning, policy making, data collection, and analysis.