By The Associated Press, via WTOP.

SAN FRANCISCO (AP) — Scott Pruitt, administrator of the U.S. Environmental Protection Agency, turned his sights this week on a nearly half-century-old federal waiver that allows California to pursue its own, tough tailpipe emission standards, and allows other states to opt in to California’s standards rather than federal ones if they choose.

The waiver has allowed California, the U.S. state with the most people and the biggest economy, to steer the rest of nation toward tougher limits on car and truck emissions that pollute the air and change the climate.