As the U.S. Supreme Court heard oral arguments on Dec. 10 in two major clean-air regulatory cases, most of the justices appeared to be sympathetic to the Environmental Protection Agency’s position that it had not exceeded its statutory powers when it issued an air-pollution-control regulation in 2011.

The cases, which the court consolidated into one proceeding, center on whether EPA overstepped its Clean Air Act authority when it issued the Cross-State Air Pollution rule in 2011. That regulation, also called the "transport rule," requires 28 midwestern and southern states to control powerplant air emissions of sulfur dioxide, nitrogen oxide and other pollutants that affect mid-Atlantic and eastern states downwind.

The cases are significant for construction, because EPA's regulation would require some $800 million annually in powerplant retrofits, mostly in upwind states, EPA has said. The rule, which a lower court suspended last year, also is estimated to save thousands of lives, according to public-health and environmental advocates.  

Judging from their comments during the 90-minute session, several justices seemed to indicate they thought EPA had not overreached. The agency finalized the regulation in July 2011 to comply with Clean Air Act requirements concerning the movement of air pollution across state boundaries.

A group of industry and labor organizations, along with Texas and several other states, challenged the regulation in a federal appellate court in 2011.

A divided U.S. Court of Appeals for the Washington, D.C., circuit vacated the transport rule in August 2012, stating that EPA had exceeded its authority in its interpretation of the 1990 “good neighbor” modifications to the clean-air statute. To take the place of the vacated transport rule, the 2005 Clean Air Interstate Rule was reinstated and remains in effect.

Justice Antonin Scalia was skeptical about EPA's position and questioned the fairness of requiring states to draw up implementation plans without knowing what the final target air-quality standards would be.

But several other justices, including Chief Justice John Roberts, seemed supportive of the arguments put forth by Deputy Solicitor General Malcolm L. Stewart, who represented EPA.

Roberts acknowledged that upwind states' task under the transport rule "is certainly hard," but, he added, "It is what the statute says, and it seems to me that if EPA had taken a different view, it would have been contrary to the statute.”

Stewart said the EPA established a process by which there could be considerable back-and-forth communication in developing either a federal implementation plan for a state or a new state plan based on EPA input.

Justice Sonia Sotomayor told Texas Solicitor General Jonathan Mitchell, who represented states opposing the rule, “You’re not prevented from giving a counter state implementation plan [SIP] … you can counter … and so it’s not clear to me that they’ve stopped you from doing your own SIP.” 

She added, “If you think they’re wrong, you give them a counter SIP, and you duke it out with them in terms of what you think.”

Justice Stephen Breyer said, “There is a procedure for the states to come in if they can come up with a better plan. … So what’s arbitrary or capricious about such a system?”

Eight justices attended the oral arguments; Justice Samuel Alito recused himself from the case.

A decision in the cases, EPA v. EME Homer City Generation and American Lung Association v. EME Homer City Generation, is expected before the end of the court's term, in June 2014.