The Supreme Court heard arguments on Nov. 7 that call into question the basic structure of federal regulation under the 1970 Clean Air Act. The cases pit the trucking industry against the Environmental Protection Agency (EPA) over whether the EPA unconstitutionally acted like a legislature when it set new, tougher emission standards for certain air pollutants on the basis of public health considerations, without considering economic costs or other factors. If the court holds that the EPA rules violated the seldom-invoked “nondelegation doctrine,” under which administrative agencies may not be given functions that properly belong to Congress, the ramifications could extend well beyond the EPA to call into question the authority of nearly all federal regulatory agencies. Even if the court shies away from such a sweeping ruling, it could still use this case to require the EPA to employ cost-benefit analyses in setting standards for emissions, something Congress has reportedly declined to do on its own. In July 1997, the EPA revised its standards to require states to reduce the level of ozone in the air from 0.12 parts per million (ppm) to 0.08 ppm, and to more tightly regulate soot particles. The agency estimated that the new rules would save an estimated 15,000 lives per year. But the trucking industry sued, claiming that the new rules would achieve these benefits at a huge cost to industry. Last year, the U.S. Court of Appeals for the District of Columbia Circuit told the EPA it would have to rewrite its rules, holding that the EPA had given no reason why it set the standards where it did, when public health would have been protected at a lower level. The court said this failure to act according to an “intelligible principle” violated the nondelegation doctrine. However, the District of Colombia Circuit held that the Clean Air Act does not authorize the EPA to set emission standards without first weighing the health benefits of its actions against their cost to industry and others.