While there is ample scholarly work on regulatory science within the state, or single-sited global institutions, there is less on its operation within complex modes of global governance that are decentered, overlapping, multi-sectorial and multi-leveled. Using a co-productionist framework, this study identifies ‘epistemic jurisdiction’ – the power to produce or warrant technical knowledge for a given political community, topical arena or geographical territory – as a central problem for regulatory science in complex governance. We explore these dynamics in the arena of global sustainability standards for biofuels. We select three institutional fora as sites of inquiry: the European Union’s Renewable Energy Directive, the Roundtable on Sustainable Biomaterials, and the International Organization for Standardization. These cases allow us to analyze how the co-production of sustainability science responds to problems of epistemic jurisdiction in the global regulatory order. First, different problems of epistemic jurisdiction beset different standard-setting bodies, and these problems shape both the content of regulatory science and the procedures designed to make it authoritative. Second, in order to produce global regulatory science, technical bodies must manage an array of conflicting imperatives – including scientific virtue, due process and the need to recruit adoptees to perpetuate the standard. At different levels of governance, standard drafters struggle to balance loyalties to country, to company or constituency and to the larger project of internationalization. Confronted with these sometimes conflicting pressures, actors across the standards system quite self-consciously maneuver to build or retain authority for their forum through a combination of scientific adjustment and political negotiation. Third, the evidentiary demands of regulatory science in global administrative spaces are deeply affected by 1) a market for standards, in which firms and states can choose the cheapest sustainability certification, and 2) the international trade regime, in which the long shadow of WTO law exerts a powerful disciplining function.