The U.S. Environmental Protection Agency can't force several Wyoming power plants to install new pollution-control equipment while the state's legal challenge to federal regulations plays out in court, an appeals court panel ruled Tuesday.

Wyoming has proposed less stringent pollution controls on coal-fired power plants than those the EPA says are required to reduce regional haze in national parks and wilderness areas. Wyoming has appealed the federal agency's rejection of aspects of its plan.

A two-judge panel of the 10th U.S. Circuit Court of Appeals in Denver on Tuesday granted a request from Wyoming and several power companies to halt implementation of the EPA rules on units at three power plants in the state while the legal challenge is pending. The facilities at issue are the Wyodak, Laramie River and Dave Johnson plants.

Gov. Matt Mead hailed the panel's decision as a victory.

"Wyoming has a solid and effective plan. The rejection of Wyoming's plan by the EPA was wrong," Mead said. "This decision sends a message to the federal government and affirms Wyoming's leadership in these important areas."

Mead said the federal Clean Air Act gives states wide discretion to meet the objectives of the law, and said the regional haze rule relates to aesthetics and not human health.

Wyoming's appeal of its regional haze plan has drawn several power companies to side with the state. The industry is eager to avoid what it says will be hefty costs of installing the pollution-control equipment the EPA rule would require.