According to a ruling by the European Court of Justice (ECJ), the emission control system for diesel engines must work at normal temperatures and for most of the year. Defeat devices that only clean emissions between 15 and 33 degrees Celsius are inadmissible, the ECJ ruled on Thursday. Because then the cleaning does not work at the usual temperatures in Europe for most of the year. According to the decision, such software constitutes “an impermissible defeat device”. Such a breach of contract is not minor, the court said. Consequently, a rescission of the purchase contract is not ruled out in principle. The legal dispute involved Austrian customers who had bought Volkswagen brand diesel vehicles between 2011 and 2013, which were equipped with fraudulent software so that the emission control only worked on the test bench. After the diesel scandal became known, Volkswagen installed an update that contained the so-called thermal window, i.e. exhaust gas cleaning depending on the temperature. The customers therefore wanted to cancel the purchase contract and get their money back against credit for use. The ECJ ruling must also be observed in Germany. The BGH wants to deal with the consequences of the ECJ’s case law in a hearing in November.