Our position is: The worst thing for both energy reliability and the environment is uncertainty over regulation of power plants.

Environmentalists are applauding a federal appeals court decision temporarily blocking the Bush administration's relaxation of Clean Air Act regulations affecting aging coal-fired power plants. But the ruling, which means more uncertainty for utilities, may prolong upgrades to aging power plants. The result: dirtier air, unsafe plants and less energy reliability.

The Clean Air Act exempted power plants and refineries built before 1970 from having to install "scrubbers" unless they made upgrades that increased emissions. Utilities and regulators have had trouble with the provision because often there isn't a clear distinction between modifications that stem from maintenance needs and upgrades that increase emissions to generate more power.

Environmentalists complain that utilities keep finding loopholes to avoid installation of pollution-control equipment. Utilities argue that the rules discourage projects such as boiler upgrades that might decrease pollution.

Under the Bush administration, the Environmental Protection Agency tried to clarify matters by saying that new pollution controls did not have to be installed if the cost of making a plant upgrade doesn't exceed 20 percent of the cost of replacing its production equipment and that any new parts were the functional equivalent of the ones being replaced.

A dozen states and several cities downwind from older Midwestern power plants appealed the rules, arguing they would increase pollution. A three-judge appeals panel has overturned the regulations until there can be a full hearing in the case, which could take a year. At issue is how much renovation the government should allow before requiring installation of new anti-pollution equipment.

Blocking the rules returns uncertainty to power plant operators and investors. That is bad for the environment and for energy reliability. Uncertainty has prevented new base-load power plant construction for decades.

The Bush administration has proposed a Clear Skies initiative that creates a flexible, market-based approach to reducing major pollutants. Even many environmentalists agree it will bring most areas of the country into compliance with the Clean Air Act. It needs to be implemented. The courts also need to expedite hearings to remove uncertainty clouding the nation's energy future.