The European Union temporarily suspended the greenhouse gas emissions allowance trading scheme for flights coming in and out of the EU, for the purpose of encouraging an agreement among members of the International Civil Aviation Organization to regulate aviation emissions. Flights between EU countries and Switzerland, however, were excluded from the suspension. Swiss International Airlines AG (Swissair) sued, claiming that the EU decision was invalid because it breached the principle of equal treatment. 

A lower court had found that the principle of equal treatment did not apply to differential treatment by the EU towards non-EU member states such as Switzerland, and that, even if the principle did apply, it had not been breached in this case. On appeal, the court found that sufficient doubt existed as to the scope of the equal treatment principle and its application in this case to justify a referral to the European Union Court of Justice, the only court with jurisdiction to declare an EU law invalid. Hearing the case on referral from the the UK Court of Appeal, the EU Court of Justice determined that, contrary to Swissair's characterization of EU law, the principle of equal treatment did not prevent the EU from excluding non-EU countries from the temporary suspension of emissions allowance trading for aircraft.