Yellowstone National Park bison do roam, and can continue to do so into Montana following a ruling Wednesday by the Montana Supreme Court.

The high court, ruling on technical grounds, rejected arguments from Park County (Montana) that a lower court erred in upholding  "Adaptive Management Adjustments" made to the Interagency Bison Management Plan in 2011 that allowed Yellowstone bison to roam further into the Gardiner Basin north of the park.

While the county in the District Court hearing claimed the AMA changes amounted to a public nuisance, that wasn't the issue it appealed to the Montana Supreme Court, noted Justice Beth Baker in the opinion. Rather, the county had argued that the lower court "violated recognized rules of statutory construction by considering the legislative history of (Montana legislation pertaining to bison) without first conducting a plain language analysis."

"Invoking our longstanding rule that a party who fails to raise a claim in the district court is barred from raising the claim for the first time on appeal, the Appellees argue that Park County’s failure to raise the plain language issue before the District Court should prevent the County from raising the issue on appeal," the opinion stated. "We have held, '[W]here a party fails to raise an issue in the pleadings, does not present argument on the issue during the hearing on the merits of the case, does not move to amend the pleadings to conform to any evidence presented and raises the issue for the first time in a post-hearing memorandum which the district court does not address in its order, the issue has not been timely raised and may not be raised on appeal.” 

The Supreme Court's ruling upholds a February 2012 decision by state agencies 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.

In a release announcing the ruling, Earthjustice attorneys, who represented the Bear Creek Council, Greater Yellowstone Coalition, and Natural Resources Defense Council in the matter, said the decision "rebuffs demands by some livestock producers and their allies to require aggressive hazing and slaughtering of bison that enter the Gardiner Basin area from Yellowstone National Park in the winter and early spring in search of the forage they need to survive."

“Today’s state Supreme Court ruling represents a victory for all those who want to see wild bison as a living part of the Montana landscape,” said Earthjustice attorney Tim Preso. “Now that the Court has rejected claims requiring bison to be slaughtered at the park’s boundaries, we can move forward to secure space for wild bison outside of Yellowstone National Park.”

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, according to Earthjustice.

Bison are the only native wildlife species still unnaturally confined to the political boundaries of Yellowstone National Park for any part of the year. As recently as 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.