Two decisions handed down last week, one by a federal court and the other by a federal agency, will have critical implications for our nation's environmental health -- and for the Bush administration's environmental legacy.

On Friday morning, a federal appeals court struck down the administration's centerpiece clean air initiative, siding with utility companies and governments that objected to parts of the Environmental Protection Agency's Clean Air Interstate Rule. The decision [PDF] by the U.S. Court of Appeals for the District of Columbia said CAIR -- which created a cap-and-trade program in the eastern United States to limit sulfur dioxide and nitrogen oxide emissions from power plants -- was unlawful because it failed to require each state to analyze its own contribution to poor air quality.

The EPA estimated that CAIR would have cut the annual number of premature deaths due to polluted air by 13,000.

Duke Energy of North Carolina was one of the plaintiffs that sued over the rule, objecting to the way it allocated permits among companies. Louisiana-based Entergy also sued, arguing that a last-minute change by the EPA required too much of oil- and gas-burning utilities and not enough from those burning coal.

But Duke -- whose CEO has forged a questionable reputation as a greener-than-average energy executive -- told the New York Times that it never meant for the entire rule to be thrown out:

Thomas Williams, a spokesman for Duke Energy, which had sued the E.P.A., contesting how the rule allocated the pollution allowances among industries, said in an e-mail message, "It was not the intent of Duke Energy's participation in this litigation to overturn E.P.A.'s Clean Air Interstate Rule."

Duke's statement about the ruling didn't assuage environmental advocates such as Southern Alliance for Clean Energy Director Stephen Smith, who blasted the company for filing suit:

"Duke Energy's rhetoric doesn't match their action. While they say they support clean air and clean power plants, they are the lead utility opposing rules that would provide the necessary reductions to protect public health and the environment. It's high time they take full responsibility for their pollution and stop getting in the way of clean air."

Joining the energy giants in opposing the rule was the state of North Carolina, which opposed the cap-and-trade approach on the grounds that it would allow some facilities to create pollution hotspots. N.C. Attorney General Roy Cooper also said he didn't want the entire rule scrapped but was pleased that the court agrees tougher rules are needed to "clean up and protect the air we breathe."

Indeed, Cooper has earned a reputation as a new kind of clean air crusader: Today marks the opening of a court trial for a groundbreaking lawsuit he brought against the Tennessee Valley Authority, charging that pollution from its facilities blows across the state lines and harms North Carolina. The suit aims to force TVA to adopt the same kind of controls North Carolina required of its own power plants in 2002.

Coming on the heels of another recent court decision striking down an EPA rule on power plant mercury pollution, Friday's ruling means all of the Bush administration's major efforts to tackle air pollution have been invalidated. Environmental Integrity Project Director Eric Schaeffer observes:

"For seven years, the Bush Administration has tried to weaken or eliminate Clean Air Act emission standards for power plants and other industries, while promising that its CAIR rule would make up the difference. That promise has proved to be hollow. The DC Circuit's decision today is only the latest in a series of rulings that have roundly rejected the Bush Administration's creative interpretations of the Clean Air Act."

In another major air quality development Friday, EPA Administrator Stephen Johnson issued a notice rejecting any regulation of greenhouse gas pollution under current law in response to a 2007 U.S. Supreme Court decision finding that such emissions from automobiles could be regulated under the Clean Air Act if they're determined to endanger the public. Johnson argues against such regulations on the grounds that they "could result in an unprecedented expansion of EPA authority that would have a profound effect on virtually every sector of the economy."

The upshot? The responsibility of limiting greenhouse gas pollution will in all likelihood be handed off to the next administration.

In the meantime, the EPA has opened a 120-day comment period on its no-action approach to greenhouse gases. For more information on the administration's position and details on submitting comments, click here.