LOS ANGELES — On April 28, the U.S. Supreme Court in-validated rules that had allowed the South Coast Air Quality Management District (SCAQMD) to require covered fleets to buy low-pollution vehicles. But SCAQMD officials maintain the ruling does not bar them from imposing the same require-ment on publicly owned fleets or on private firms that provide city services — a contention hotly disputed by the engine manufacturers that prevailed in the lawsuit, according to an article in the Los Angeles Times. Diesel engine manufacturers, among others, sued the SCAQMD because it had barred private fleets from buying their products in the greater Los Angeles area, despite advances in clean diesel technology. The 8-1 decision by the U.S. Su-preme Court said that the SCAQMD had overstepped its au-thority under the Clean Air Act. The decision should clear the way for covered fleets bound by the rule to buy new diesel engines that emit far less pollution than older models. But SCAQMD District officials firmly maintain that the new diesel engines, although improved, are still far from clean compared with alternatives such as engines that burn natural gas, according to the L.A. Times article. The U.S. Supreme Court said that the SCAQMD could still impose fleet rules by receiving the approval of the California Air Re-sources Board as well as the U.S. Environmental Protection Agency. The SCAQMD said it would seek such approvals.