HOT AND COLD.(The Talk of the Town)

Thirty-six years ago this month, President Nixon signed the Clean Air Act in a ceremony in the Roosevelt Room of the White House. The act--the product of a bipartisan effort extraordinary even for a day when bipartisanship was unexceptional--had been hammered out by a group of senators that included Democrats Edmund Muskie, Birch Bayh, and Thomas Eagleton, and Republicans Bob Dole, Howard Baker, and Robert Packwood. The bill passed the Senate unanimously, prompting Senator Eugene McCarthy to tell Muskie, "Ed, you finally found an issue better than motherhood." At the signing ceremony, Nixon called the Clean Air Act a "historic piece of legislation," but he stressed that it was only a first step. "I think that 1970 will be known as the year of the beginning," he said.

Nostalgia for the Nixon Administration is an increasingly acceptable emotion these days, and it was hard not to feel it last week, when oral arguments were heard in Massachusetts v. Environmental Protection Agency. The suit, which has been described as "one of the most important environmental cases ever," is the first on global warming to reach the United States Supreme Court. The plaintiffs--a group that includes, in addition to Massachusetts, eleven states, three cities, and thirteen environmental groups--hope to compel the Bush Administration to impose limits on greenhouse-gas emissions. If they are successful, the operation of every power plant and factory as well as the design of every new car in the country could potentially be affected. At the center of the suit is the Clean Air Act, and the question of just how ambitious its authors intended it to be.

The Bush Administration's position, in keeping with its general stance toward regulation but in contrast to its general stance toward executive power, is that its hands are tied. The E.P.A., it argues, lacks the authority to limit greenhouse gases under the Clean Air Act, because when the act was drafted global warming wasn't yet recognized as a problem. The "relevant provisions of the law," it states in its brief to the Supreme Court, are "best construed not to authorize regulation . . . for the purpose of addressing global climate change." Furthermore, the Administration asserts, even if the Clean Air Act did grant the E.P.A. the power to treat CO2 as a pollutant, the agency shouldn't--and wouldn't--exercise it.

Just about anyone familiar with the Clean Air Act can see the White House's narrow reading of the law for what it is: a deliberate misreading. The act was expressly constructed to allow the E.P.A. to regulate substances known to be dangerous and also substances that might in the future be revealed to be so. Danger was defined as broadly as possible; among the many possible hazards listed in the statute are "effects on soils, water, crops, vegetation, manmade materials, animals, wildlife, weather, visibility, and climate." In a friend-of-the-court brief for the plaintiffs, four former E.P.A. administrators--including Russell Train, who headed the agency under Nixon, and William Reilly, who led it under George Bush senior--point out that Congress clearly directed the E.P.A. to "regulate air pollution ...