Carbon markets have provided fertile ground for research on the changing nature of political contestation. MacKenzie locates a “techno‐politics” of carbon markets that creates new possibilities for a “politics of market design”. In contrast, Swyngedouw argues carbon markets are part of a “post‐political” shift that narrows potential pathways through “depoliticisation”. This article engages with these debates by examining three recent attempts to reform the ailing European Union Emissions Trading System: restricting industrial gas offsets, backloading allowance auctions and the 2030 climate and energy package. It conceptualises the respective episodes as contests over the reach, force and priority of value determinations in climate policy, emphasising the contradictory imperatives facing states on each issue. The outcomes of contestation between industry groups and environmental organisations—real but limited reforms and a consolidation of the carbon market over alternatives—demonstrate the constraints facing technocratic campaigning and the ongoing politicisation of climate change.