A watchdog group has filed a lawsuit in a Montana court that could change the way the U.S. Forest Service uses fire retardant to battle blazes nationwide. The Forest Service Employees for Environmental Ethics, based in Eugene, Ore. filed a lawsuit in U.S. District Court in Missoula, Mont. earlier this week. The lawsuit challenges the Forest Service's compliance of a 2005 ruling that set regulations in place for the use of fire retardant. Dumping fire suppression chemicals above lakes and streams has a detrimental effect on fish, said Andy Stahl, executive director of the group. He noted the death of …