A federal judge in Los Angeles has upheld rules by the Diamond Bar, Calif.-based South Coast Air Quality Management District (SCAQMD) that require public fleets to purchase lower-emission vehicles when buying new trucks and buses. The Chicago-based Engine Manufacturers Association and the Sacramento, Calif.-based Western States Petroleum Association challenged the rules and have said they are considering appealing the decision, which was issued by U.S. District Judge Florence-Marie Cooper in May.

In April 2004, as part of the two associations’ legal challenge, the U.S. Supreme Court ruled that the federal Clean Air Act pre-empts portions of the fleet rules. Therefore, the rules could not be applied to privately owned fleets, the high court said. The Supreme Court then remanded the case back to Cooper to decide other issues. An SCAQMD spokesman told The Associated Press that the agency believes that the ruling applies to private fleets that contract with local governments, but noted that Cooper’s ruling did not specifically address that question.