Washington, D.C. –- Supreme Court justices are considering whether Los Angeles may impose anti-smog rules that are tougher than the federal Clean Air Act. The city’s regulations currently apply to buses, airport shuttles, taxis and other vehicles -- such as garbage trucks. Oil companies and diesel-engine manufactures have argued that the anti-smog rules conflict with national standards. However, the city and counties to which the rule applies have the worst air-quality in the nation: Los Angeles; San Bernadino, Riverside and Orange counties. This year, the Supreme Court is hearing eight environmental cases, which is considerably more than usual.