There has been a sharp increase in the amount of litigation regarding the European Union Emissions Trading Scheme in recent years. Cases revolve mainly around the limits of the Commission’s discretion in reviewing National Allocation Plans (NAPs). This may seem a mere technicality; however, as this article aims to show, it is better described as an undercurrent of legal challenges relating to the allocation of authority between the Member States and the Commission in this particular climate change regime. By examining four cases in particular – United Kingdom v Commission, Germany v Commission, Poland v Commission and Estonia v Commission – attention to these issues will be brought to light, and the idea of caps being simply instrumental in emissions trading refuted.