Two recent Supreme Court cases could change the way the EPA handles some of the nation’s air pollution issues.

In a 5-4 decision, the court rejected a position of the Bush Administration that greenhouse gas emissions did not constitute pollutants as defined in the Clean Air Act. The Supreme Court majority decided U.S. motor-vehicle emissions make a “meaningful contribution to greenhouse gas concentrations” and hence, to global warming. Further, the court ordered the EPA to reevaluate its contention that it has the discretion not to regulate greenhouse gas emissions, noting that arguments should be tied to the Clean Air Act.

The second case decided in early April closed a potential loophole in the Clean Air Act’s New Source Review (NSR) provisions. The decision involved Duke Energy, a North Carolina company that updated air pollution control systems at its coal-fired power plant during the late 1980s and early ‘90s. While the upgrades did not raise the company’s hourly emissions, they did allow the facility to run for more hours each day. The environmentalist organizations who brought suit claimed this accounted for an increase of emissions, making the plant subject to the permitting process of NSR. Duke Energy contended that EPA enforcement of NSR was vague, and that by remaining under their hourly standard, a permit for the upgrades was unnecessary. The court overturned a previous ruling in favor of Duke Energy, remanding the case back to the district court for consideration. The justices found that when the 4th U.S. Circuit Court of Appeals in Richmond, Va., ruled in favor of Duke that it negated EPA emissions regulations, which it did not have the authority to do.