BRUSSELS (Reuters) - Technologies used by Volkswagen to rig vehicle emissions tests should be considered illegal, the European Union’s highest court ruled on Thursday, even if they contribute to preventing ageing or clogging up of the engine. The Court of Justice of the European Union was asked to rule in a French prosecution against the carmaker for allegedly deceiving purchasers of diesel vehicles. Volkswagen had argued in favour of a restrictive definition of devices used to rig emissions tests, limited to technologies and strategies operating only “downstream”, or after potential emissions are produced. However, the court found that the term should also apply to “upstream” technology. Use of so-called defeat devices to help a vehicle pass emissions tests is illegal under EU law. The French case concerned an exhaust gas recirculation (ERG) valve, which can redirect some exhaust gases back into the air supply for the engine to reduce final NOx emissions. The ERG was adjusted in tests using a device to allow emissions to remain below the regulatory ceiling, but according to an expert’s report the device would in normal conditions lead to the partial deactivation of the ERG and higher NOx emissions. Operation of the ERG would have made maintenance more frequent and expensive because, for example, the engine would clog up more quickly. Volkswagen said that the court’s opinion on the classification of the ERG had no consequences on legal proceedings regarding its diesel cars, in Germany or elsewher “In the legal disputes still ongoing outside of Germany, the outcome ultimately depends on the question of possible damage to the vehicle keepers concerned,” it said in a statement. Volkswagen announced recalls of almost 950,000 vehicles in France following the “dieselgate” scandal in which it admitted in 2015 to using illegal software to cheat U.S. diesel engine tests. The scandal has cost Volkswagen more than $30 billion in vehicle refits, fines and provisions.