The decision could have nationwide implications, allowing local governments to set higher pollution standards and making some engines unusable in their areas.
The rules, adopted in 2000 and 2001 by the South Coast Air Quality Management District, were intended to replace local government diesel-fueled buses, street sweepers, trash trucks and airport shuttles with cleaner-burning models.
Counsel for the clean air agency argued that it was within its legal authority to impose stricter rules to improve air quality. Seth Waxman, representing the district, told justices the rules don't conflict with federal regulations, because they do not force manufacturers to change emission standards. They merely give guidance to fleet operators to buy cleaner-burning vehicles that are already on the market. He told the court: "They [the rules] cannot be read to require manufacturers to make anything they don't make.”
Lawyers for oil companies and diesel engine makers contend that local pollution rules in this instance conflict with the federal Clean Air Act and that federal law must prevail. Lawyers for the Engine Manufacturers Association Engine Manufacturers Association and the Western States Petroleum Association said that there would be chaos if each state or every local jurisdiction set its own standard.
Several industry groups involved with transportation joined EMA and WSPA in bringing the case to the Supreme Court including the Alliance of Automobile Manufacturers, American Petroleum Institute, American Trucking Associations, National Petrochemical Refiners Association, National Manufacturers Association, National Automobile Dealers Association, Truck Manufacturers Association and the United States Chamber of Commerce.
The air quality district covers parts of Los Angeles, Orange, Riverside and San Bernardino counties and is supported by the National League of Cities, other local government agencies and 16 states.
The case is Engine Manufacturers Association v. South Coast Air Quality Management District.