The Supreme Court on Wednesday left in place a rule issued by the Environmental Protection Agency in May to reduce emissions of carbon dioxide by power plants. In a brief order, the justices turned down a request from states, energy companies, and other industry groups to put the rule on hold while their challenge in a federal appeals court moves forward.

Defending the rule, the EPA says that it would lead to significant reductions in carbon pollution over the next two decades – “equivalent to preventing the annual emissions of 328 million gasoline cars.” And that in turn, the EPA argues, could provide nearly $400 billion in benefits to the climate and public health.