This article examines the recent judgment in case C-366/10 in which the CJEU upheld the widened scope of the EU Emissions Trading Scheme, to include aviation, against a challenge by US airlines. At the core of this case stands the question of the extent to which, if at all, the EU is allowed to unilaterally control greenhouse gas emissions from aviation given that to date these are unregulated at an international level. As such, this is a case concerning the legitimacy of regional regulatory responses to global institutional failings. What the court does is to legitimise EU’s leading role in combating climate change, which has important implications not only with regard to EU’s climate change policy but also in shaping the global climate change regime.