Attorneys for environmental groups and a major utility battled before the Supreme Court over a Clean Air Act provision that deals with when emissions from powerplants that undergo modifications are large enough to require upgraded pollution-control systems. It's unclear whether the court's decision, expected by next summer, will have a broad effect on the clean air statute or be focused narrowly on regulatory details.
During oral arguments on Nov. 1 in the case, Environmental Defense v. Duke Energy Corp., the justices quizzed lawyers for both sides about the complexities of definitions of terms in U.S.Environmental Protection Agency regulations stemming from the clean air law's "New Source Review" provisions. That program requires powerplant and factory owners to install up-to-date emissions-control equipment when they make modifications to their facilitie that increase emissions. Parties in the case differ on what the regulatory definitions of "modifications" and "increase" are.