By Lawrence Hurley

WASHINGTON, Dec 23 (Reuters) - A U.S. appeals court on Tuesday handed environmental groups a win by throwing out federal regulations that gave local government agencies more leeway in meeting air quality standards for ozone.

In a 2-1 decision, a three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit ruled against the U.S. Environmental Protection Agency on both of the legal questions raised by the Natural Resources Defense Council.

The case concerns the EPA's plans to implement ozone air standards under a 2008 regulation.

The court found fault with the EPA's plan to allow local districts more time to meet the new standards than allowed under the Clean Air Act.

The court also threw out the EPA's plan to give local districts more leeway to plan transportation projects, which the challengers said would lead to a rise in ozone emissions.

Both of the EPA's proposals "exceed the agency's authority under the Clean Air Act," wrote Judge Sri Srinivasan on behalf of the court. The case does not affect the underlying 2008 ozone rule.

Judge Raymond Randolph wrote a dissenting opinion saying the court's decision was "a mistake in judicial analysis" that will create significant headaches for both the EPA and states.

The case is NRDC v. EPA, U.S. Court of Appeals for the District of Columbia Circuit, No. 12-1321. (Reporting by Lawrence Hurley; Editing by Mohammad Zargham)