Unusually, the commission acted on its own, without a complaint from the European auto industry. Industry leaders and Germany, home to BMW, Volkswagen and Mercedes-Benz, have opposed the tariffs. That’s because many of the cars that will be hit with tariffs are made by European companies, and China could retaliate against the auto industry or in other areas.

Beijing has been sharply critical of the investigation and the higher duties as protectionist and unfair.