California’s authority to set environmental rules that are tougher than national standards had never been challenged by Congress. Until now.

Dozens of states follow CARB's stringent regulations, but new moves by the Senate threaten California's emissions-setting independence.

The US Senate voted today to strip California of its authority to enact state limits on tailpipe pollution that are tougher than national standards. Opponents called it an illegal move by Republican lawmakers that flies in the face of Senate rules and norms.