The Environmental Protection Agency (EPA) exceeded its authority under the federal Clean Air Act when it promulgated the Cross-State Air Pollution Rule (CSAPR) in 2011, nine states argue in a brief filed with the U.S. Supreme Court last week.

The brief filed by a bipartisan group of attorneys general from Arizona, Arkansas, Kentucky, Missouri, Montana, North Dakota, South Dakota, West Virginia, and Wyoming is the latest filing in EPA v. EME Homer City Generation, a much-watched case that will decide whether, as the EPA contends, the D.C. Circuit exceeded its jurisdiction when it vacated the rule in August 2012. Oral arguments are set for Dec. 10, and a decision is expected by next June.

The EPA and other parties including the American Lung Association argue in their petitions for certiorari that various challenges to CSAPR are foreclosed by prior EPA actions, including the rule-making proceedings and EPA orders finding substantial noncompliance by the relevant states. The government also argues that the D.C. Circuit decision, “if left undisturbed, will gravely undermine the EPA’s enforcement of the Clean Air Act.”

Backed by 15 other states as well as industry groups who sued the EPA on the same issue in 2011, the attorneys general of the nine states argue that when Congress established the Clean Air Act, it adopted a cooperative federalism structure to gives states and the federal government specific roles. “EPA’s job is to use federal resources to identify air pollution problems and set goals for cleaner air. The States’ job is to achieve those goals while working through local problems and conditions,” the brief says. Congress also gave the states “wide discretion in developing implementation plans and sharply limited EPA’s ability to reject proposed state implementation plans,” it says.

But by promulgating the CSAPR, the EPA “turned this structure on its head and departed from its own longstanding view of the Act,” the states say. The EPA has contended that because the states failed to quantify the amount of cross-state air pollution in each state, it has the right to take the lead on implementation and impose a federal plan.

“EPA’s novel theory is not only backwards, but an attempt to shut out the States entirely,” the states argue. One reason is that it is “impossible” for the states to quantify cross-state air pollution for regional pollutants. “The effort would require a massive and unprecedented multi-state collaboration, necessitating the cooperation of at least thirty States with competing interests, as well as significant money, expertise, and technology.” Even if the states could manage that, they argue, the EPA “claims to have an effectively unlimited veto over the state’s conclusions.”

“Our Office is very concerned about the Environmental Protection Agency’s cross-state air pollution rule targeting coal- and natural gas-fired power plants,” said West Virginia Attorney General Patrick Morrisey in a statement. “The agency’s rule imposes one-size-fits-all federal plans on power plants and utilities, costing them $2.4 billion per year to comply. This issue is something that I thought our office should have been involved in fighting aggressively when the regulations were announced, and I believe this step will help protect West Virginia’s interests.”

Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)