WASHINGTON — The Supreme Court heard arguments on Tuesday in a knotty environmental case over how to hold states responsible for air pollution that drifts across their borders and causes harm in downwind states.
If there was consensus among the justices, it concerned only the complexity and difficulty of the issues before them.
“This is a tough problem,” Justice Stephen G. Breyer said. A few minutes later, Justice Elena Kagan offered a similar assessment. “This is a hard problem,” she said.
Still, the questioning suggested that there may well be five votes to sustain the Environmental Protection Agency regulations at issue. “It’s certainly hard,” Chief Justice John G. Roberts Jr. said of the task of allocating responsibility, “but it is what the statute says, and it seems to me that if E.P.A. had taken a different view, it would have been contrary to the statute.”
Justice Anthony M. Kennedy also asked questions suggesting support for the regulations. “It seems to me that in some respects the E.P.A. is more constrained under this process to which you object,” he told Jonathan F. Mitchell, the solicitor general of Texas, who represented 14 states challenging the rules.
The agency’s approach, which involves a trading system for pollution credits, was struck down last year in a 2-to-1 ruling from the United States Court of Appeals for the District of Columbia Circuit. The appeals court said the agency had exceeded its authority under the Clean Air Act in the way it apportioned the cleanup work among 28 upwind states.
The air in those states, mostly in the Midwest and the South, may meet regulatory standards within their borders even as pollutants from their power plants and refineries drift across state lines, preventing neighboring states from meeting their legal obligations. The affected states are largely in the Northeast and the mid-Atlantic.
The regulation at issue, the Cross-State Air Pollution Rule, sometimes called the transport rule, did not apportion reductions by the amount of pollution contributed by each upwind state. Instead, the agency sought to encourage remedial action where it was cheapest.
The appeals court said that this approach violated the Clean Air Act’s “good neighbor” provision by requiring upwind states “to reduce their emissions by more than their own significant contribution” to downwind pollution.
Much of Tuesday’s arguments concerned whether the agency could take cost into account or whether, as Justice Kagan put it, “Congress has demanded that the regulation occur in a fundamentally silly way.”
Justice Antonin Scalia said that cost-based regulations might be wise policy, “but it’s certainly not the statute that Congress wrote.”
Peter D. Keisler, a lawyer for industry and labor groups challenging the regulations, said they were flawed because “there is no relationship at all under the E.P.A.’s methodology between the amount a state contributes and the amount it has to reduce.”
Justice Kagan responded that the agency had taken a sensible approach. “What the E.P.A. said here was, ‘We’re going to distinguish between states that have put a lot of technology and a lot of money into this already and, on the other hand, states that have lots of cheap and dirty emissions.’ ”
The agency has said that exposure to ozone and fine particles was responsible for one in 20 deaths in the United States, 200,000 nonfatal heart attacks, 90,000 hospital admissions and 2.5 million cases of aggravated asthma among children.
The appeals court also overturned the regulation on a second ground, saying it was flawed because it did not let the states submit their own plans to comply.
In its Supreme Court brief, the environmental agency said the complexity of the problem justified its approach. “The interstate pollution problem is best understood,” the brief said, “as a dense, spaghetti-like matrix of overlapping upwind/downwind ‘linkages’ among many states, rather than a neater and more limited set of linkages among just a few.”
Chief Justice Roberts said Tuesday that the matrix analogy meant there was no way for “the state to know how much of a burden you expect them to address.”
Malcolm L. Stewart, a deputy solicitor general representing the environmental agency, seemed to engage the court by asking what the phrase “contributes significantly,” used in the Clean Air Act, might mean to a basketball coach who had just lost a game.
Chief Justice Roberts appeared taken by the idea, saying, “If you ask the coach what significantly contributed to the loss, he’s going to talk about the missed layup rather than the missed desperation throw, even though as far as amount, each was going to count for two points.”
Mr. Keisler declined to talk about basketball. But Justice Scalia said that every point in a game has the same value.
The argument lasted 90 minutes, instead of the usual hour. Justice Samuel A. Alito Jr. disqualified himself, presumably over a financial conflict. That left open the possibility of a 4-4 tie in the case, Environmental Protection Agency v. EME Homer City Generation, No. 12-1182. A tie would leave the decision of the appeals court in place.
Also Tuesday, the court dismissed a case that could have resolved a dispute among the lower courts on deals in which employers aid unionization drives in exchange for labor peace, called “neutrality agreements.” The federal appeals court in Atlanta ruled that such deals can run afoul of a federal labor law that bars employers from giving a “thing of value” to unions.
The court’s unsigned one-sentence decision in the case, Unite Here Local 355 v. Mulhall, No. 12-99, gave no explanation for the dismissal, which followed an oral argument last month.
In a dissent, Justice Stephen G. Breyer said questions had arisen about whether the case was moot and whether the worker who brought the suit had suffered the sort of injury that gave him standing to sue. Justice Breyer, who was joined by Justices Kagan and Sonia Sotomayor, said the court should have asked for further briefs rather than dismiss the case and leave in place an appeals court decision that “could negatively affect the collective-bargaining process.”