Bison are the only native wildlife species still unnaturally confined to the political boundaries of Yellowstone National Park for any part of the year. In 2008, more than 1,400 bison—about one-third of the current size of Yellowstone’s bison population—were captured and slaughtered by government agencies while leaving Yellowstone in search of food.

Federal and state agencies responsible for cooperatively managing bison around Yellowstone National Park decided in February 2012 to allow bison seasonal access to important winter and early spring habitat outside the north boundary of the park in the Gardiner Basin area until May 1 of each year. Their decision opened up critical foraging lands during a period when higher elevations in the park still lack spring grasses for bison and other grazing animals.

However, in two lawsuits filed in May 2011, the Park County Stockgrowers Association, Montana Farm Bureau Federation, and Park County, Montana, sought to block implementation of the new policy and require state officials to adhere to outdated plans for bison hazing and slaughter. Although the plaintiffs in the cases raised concerns about the potential for bison to infect cattle with brucellosis, the only two cattle ranchers operating year-round in the Gardiner Basin did not join the legal challenge.

Earthjustice stepped into the case to defend the new bison tolerance policy on behalf of the Bear Creek Council, Greater Yellowstone Coalition, and Natural Resources Defense Council. In January of 2013, a Montana judge rejected the challengers’ lawsuits and upheld the new state policy allowing wild bison room to roam outside the northern boundary of Yellowstone National Park. The judge’s decision followed five days of trial during which many Gardiner Basin residents voiced their support for bison tolerance in the area.

In March of 2014, the Montana Supreme Court reaffirmed that bison can roam free.