The EU Emissions Trading Scheme Directive (2003/87/EC) established a scheme for greenhouse gas emission trading within the European Union. In 2008 the European Parliament and the European Council adopted the EU Aviation Emissions Trading Scheme Directive (2008/101/EC) to bring aviation activities within the scope of the EU scheme. Under the latter directive, from January 1 2012, all aircraft that arrive or depart from EU airports will be subject to a cap on their carbon dioxide emissions.This is being opposed by several airlines and airline associations whose headquarters are in the United States of America (USA) or Canada. They are challenging in the High Court of Justice of England and Wales the measures taken by the United Kingdom to implement Directive 2008/101. They submit that by including international aviation – and transatlantic aviation in particular – in its emissions trading scheme, the European Union is in breach of a number of principles of customary international law and of various international agreements.The High Court of Justice of England and Wales, Queen’s Bench Division, asked the ECJ to give a preliminary ruling on the validity of Directive 2008/101.In her opinion delivered on Oct. 6, 2011, Advocate General Kokott came to the following conclusion:Of the provisions and principles of international law mentioned in the first question referred for a preliminary ruling, only Article 7 and the second sentence of Article 15(3) of the Air Transport Agreement concluded in April 2007 between the European Community and its Member States, of the one part, and the United States of America, of the other part, can be relied upon as a benchmark against which the validity of acts of the European Union can be reviewed in legal proceedings brought by natural or legal persons.Consideration of the questions referred has disclosed no factor of such a kind as to preclude the validity of Directive 2003/87/EC as amended by Directive 2008/101/EC.The opinion is not binding. Though reasoning of such opinions tends to be followed in most cases, it is not exceptional for the court to disagree.Full text of opinion in Case C‑366/10 (The Air Transport Association of America and Others) available here>>.