A federal appeals court on Friday threw a wrench into the Clinton administration’s plans to tighten air quality regulations, ruling that the EPA overstepped its authority by adopting new standards for ozone and particulates in 1997. The judges found that the EPA’s actions were unconstitutional and that the agency had failed to show that the additional health protections were justified. The EPA continues to maintain that the standards would improve the health of millions of Americans, and it quickly announced that it would appeal the ruling. Oil industry lawyers claim the new ruling could put a halt to the administration’s plans, outlined this month, to require cleaner gasoline and automobiles, but the EPA disagrees and will continue with its plans.