The Trump administration today revoked California’s power to set higher fuel efficiency standards for automakers than the federal government—an authority formally given to the state by Congress under the Clean Air Act. Notoriously plagued by air pollution, California has long been a leader in reducing smog-forming tailpipe emissions. When the U.S. Environmental Protection Agency proposed gutting clean car standards last summer, the state could still keep its more protective pollution standards in place. Not anymore. In addition to California, which has the nation’s largest auto market, Trump’s move affects the stronger fuel efficiency standards for 13 other states. All told, the reversal will affect 35 percent of the passenger vehicle market, resulting in lower air quality for 118 million Americans and more planet-warming pollution. Americans will also end up paying more at the pump while automakers face increasing regulatory uncertainty. It’s a lose-lose-lose-lose kind of deal.