The decision was a result of a lawsuit brought by conservation groups who argued that the Department of Energy has shirked its responsibility to reduce foreign oil dependence, global warming and air pollution.

A federal judge agreed, ruling that the Energy Department failed to adhere to a requirement from Congress that it consider imposing an alternative-fuel-vehicle purchasing requirement on private and municipal fleets.

The ruling, by District Court Judge William Alsup, does not force the Energy Department to impose a requirement on municipal and private vehicle fleets to purchase more alternative-fuel vehicles. However, the decision would require the department to engage in a two-step rulemaking process during which it would consider imposing such a requirement.

The judge issued the decision March 6. He ordered both sides to submit ideas to the court for establishing a timetable for future Energy Department actions.