A summary of this morning’s Supreme Court decision in Massachusetts v. EPA, from SCOTUSblog:

Ruling 5-4, the Supreme Court on Monday found that the federal government had the authority to regulate greenhouse gases that may contribute to global warming, and must examine anew the scientific evidence of a link between those gases contained in the exhausts of new cars and trucks and climate change. In the most important environmental ruling in years, the Court rebuffed the Environmental Protection Agency’s claim that regulating those gases was beyond its authority, and the agency’s claim that it need not take action even if it did have the power to do so. Justice John Paul Stevens wrote for the majority.

The benchslap came when the Court ordered the EPA to reevaluate its decision not to regulate carbon dioxide emissions. From the Associated Press:

The court had three questions before it.

– Do states have the right to sue the EPA to challenge its decision?

– Does the Clean Air Act give EPA the authority to regulate tailpipe emissions of greenhouse gases?

– Does EPA have the discretion not to regulate those emissions?

The court said yes to the first two questions. On the third, it ordered EPA to re-evaluate its contention it has the discretion not to regulate tailpipe emissions. The court said the agency has so far provided a “laundry list” of reasons that include foreign policy considerations.

The majority said the agency must tie its rationale more closely to the Clean Air Act.

“EPA has offered no reasoned explanation for its refusal to decide whether greenhouse gases cause or contribute to climate change,” Stevens said.

EPA Administrator Stephen Johnson was also ordered to write “I will not make fun of Al Gore” three hundred times on a blackboard.
Justices: EPA Can Control Car Emissions [AP via Washington Post]
EPA must consider global warming again [SCOTUSblog]
Massachusetts v. EPA (opinion; PDF) [SCOTUSblog]