By MATT VOLZ
HELENA, Mont. (AP) -- A federal judge has blocked Montana officials from using a helicopter to drive bison back into Yellowstone National Park.
U.S. District Judge Charles Lovell's temporary restraining order Monday follows arguments by wildlife advocates that federal and state officials had not properly studied how the use of helicopters affects grizzly bears.
Grizzlies are threatened under the federal Endangered Species Act, and the Alliance for the Wild Rockies says the flights can drive bears from their habitat.
Attorneys for the state and federal defendants say the Interagency Bison Management Plan calls for a halt to hazing operations when they encounter a grizzly.
The Montana Department of Livestock twice last week hazed bison with a helicopter. Officials had planned one more operation on Tuesday for 70 bison that remain in the Hebgen basin.
Copyright 2012 The Associated Press.