In a preliminary ruling on Air Transport Association of America v. Energy Secretary, the Court of Justice of the European Union delivered a groundbreaking decision. The case is concerned with the legality of the inclusion of the aviation sector in the EU emission trading scheme (ETS). As such, it poses many interesting legal questions from the points of view of EU external relations and EU environmental law, but ultimately what the case represents is a resounding victory for the EU and its Member States in confirming the legality of the inclusion of aviation in the EU ETS.