In a 2-1 decision, the U.S. Court of Appeals for the District of Columbia Circuit threw out a two-year-old rule that may have allowed some refineries, power plants and factories to exceed pollution limits because the Environmental Protection Agency "failed to fix inadequate monitoring requirements ... and prohibited states and local authorities from doing so."

Since 1990, the Clean Air Act has required permits granted to facilities releasing more than 100 tons of any pollutant a year to include enough monitoring to ensure the company is meeting its emissions targets. Approximately 15,000 to 16,000 permits have been issued under the program, mostly by state and local pollution agencies.

"We can't have strong enforcement of our clean air laws unless we know what polluters are putting into the air," said Keri Powell, a staff attorney with Earthjustice, who sued the EPA on behalf of four environmental groups.

The EPA said Tuesday that it was reviewing the court's decision. But an agency spokesman said the monitoring deficiencies should be remedied on the national level rather than on a case-by-case basis.

Appeals court judge Brett Kavanaugh, a former attorney in the Bush White House, wrote the sole dissenting opinion.

He said that while EPA and state and local governments may disagree about whether monitoring requirements will adequately measure compliance, he found "nothing in the statute that prohibits EPA's approach."