WASHINGTON — In trying to decide whether the Environmental Protection Agency has the authority under two programs to regulate greenhouse gas emissions from stationary sources like power plants, the Supreme Court on Monday faced what Justice Elena Kagan called “the conundrum here.”
One part of the Clean Air Act, she said, seemed to require that such emissions be regulated. But another part set the emission thresholds so low that even schools and small businesses would be covered.
The agency’s solution was to raise those thresholds, and the resulting standards covered far fewer sources. That move was at the center of Monday’s arguments, and the justices seemed divided along ideological lines over whether it was a sensible accommodation or an impermissible exercise of executive authority.
Justice Anthony M. Kennedy, who may hold the decisive vote, made a point that did not bode well for the agency.
“I couldn’t find a single precedent that strongly supports your position,” he told the agency’s lawyer, Donald B. Verrilli Jr., the U.S. solicitor general.
Verrilli said the solution to the conundrum was to allow the agency to exercise some discretion.
“The choice,” he said, “is between throwing up your hands with respect to what EPA considers to be the most serious air pollution problem we have or trying to deal with the implementation problem.”
But Justice Samuel A. Alito Jr. suggested that the agency’s revision of numerical standards in a statute was without precedent in “the entire history of federal regulation.”
Even as the justices differed on the scope of the agency’s authority, though, they seemed to agree that the case before them was not particularly significant, for two reasons.
First, the narrow issue the Supreme Court agreed to address left in place the agency’s determinations that greenhouse gases present an urgent threat and that emissions from motor vehicles may be regulated.
Those determinations were based on the Supreme Court’s 5-to-4 decision in 2007 in Massachusetts v. Environmental Protection Agency, which required the agency to regulate emissions of greenhouse gases from new motor vehicles if it found that they endangered public health or welfare.
At Monday’s argument, the justices did not seem inclined to re-examine that decision. Indeed, Kennedy, who was in the majority, said, “We’re bound by both the result and the reasoning of Massachusetts v. EPA.”