In one of its most significant environmental decisions in years, the U.S. Supreme Court today rejected industry arguments and unanimously upheld the way the federal government sets clean air standards. The trucking and manufacturing industries argued that the U.S. EPA should consider compliance costs and not just health benefits in setting the standards. But Justice Antonin Scalia wrote in the court opinion that the Clean Air Act “unambiguously bars cost considerations.” The high court also ruled that the section of the act on which the EPA relied in reaching standards for ozone and particulate pollution in 1997 did not amount to an unconstitutional delegation of legislative power from Congress to the executive branch. However, in a third part of the ruling, the court said that the EPA’s implementation plan for the ozone standard was unreasonable and must be revisited.