March, 2014: The Montana Supreme Court has ruled that bison can temporarily roam outside the Yellowstone Park boundaries during winter without being killed. The bison often cross Park boundaries during harsh winters when the lower elevation in Montana offers grass for grazing. They return to the Park when the snow thaws.
This ruling upholds a February 2012 decision by lower state agency courts. In 2012, livestock producers and their allies countered the original decision by demanding aggressive hazing and slaughtering of bison that enter the Gardiner, Montana area in the winter. Their fears are that bison could infect domestic cattle. About half of Yellowstone's 4,600 bison test positive for brucellosis, which causes pregnant animals to prematurely abort their young. Bison advocates speculate that this is not the real issue because elk with brucellosis present a much bigger threat to livestock than bison.
Now, this affirmation of the courts clearly states that slaughter of these roaming animals is illegal, even outside the Park
(Above video by Leo Leckie) March 14, 2014 -- This herd of Yellowstone National Park Bison dashes from Mammoth Hot Springs eastward along the roadway and deeper into the park. If the herd matriarch gets the urge to run, she will ... and the entire herd will run to keep up. Sometimes I can tell, I can feel that this running is a celebration of life -- running for the sheer joy of being able to. (YouTube)