In the agri-food sector global sustainability partnerships play an increasing role in setting and enforcing certification standards through global value chains. Amidst perception that the capacity of states to steer sustainable transnational forms of production is diminishing, these partnerships are increasingly led by firms and non-firm actors. Using the case of the Parties to the Nauru Agreement (PNA) Marine Stewardship Council (MSC) certification of free school skipjack tuna purse seine fisheries, this paper challenges this idea of diminished state agency by exploring how these states are repositioning themselves in the global tuna value chain. We document how PNA created the conditions for its small island member states to use the MSC certification for expanding their role as the owner of tuna resources and becoming global value chain actors themselves through a novel and disruptive public–private partnership. The results indicate that states can use market demand for certified tuna to improve their position as both producers and intermediaries in the chain, and in doing so recapture greater sovereign control over tuna resources while improving their capacity for domestic wealth generation.