A federal judge rejected the National Park Service’s (NPS) request to pause a lawsuit challenging the agency’s management of bison in Yellowstone National Park.
A 2024 NPS bison management plan in the Greater Yellowstone Area drew a pair of lawsuits from the state of Montana and two conservation groups, Alliance for the Wild Rockies and Council on Fish and Wildlife. The two suits have since been consolidated.
While the state of Montana alleged NPS failed to consult the state on the plan and the potential impacts from brucellosis to cattle, the conservation groups contended the plan did not use the best available scientific analysis.
The Department of the Interior and NPS requested a stay on the litigation pending a supplemental environmental impact statement (SEIS). The feds said a supplemental review is warranted because “seasonal bison migration out of the park has become less predictable in timing and duration” and “this change affects the reliability of management assumptions that informed the 2024 analysis,” according to court documents.
NPS further said that the agency would determine “whether additional analysis of any issues raised in (the Alliance and Montana lawsuits) is appropriate, and if so, will include such analysis in the SEIS.”
While the state of Montana did not oppose the stay, the conservation groups did, arguing that an SEIS would not address the groups’ claims. A hearing was held on the matter on June 22.
Judge Brian Morris of the U.S. District Court for the District of Montana denied the federal government’s stay request on July 21.
“A stay would fail to simplify the proof or questions of law at issue in this case,” Morris wrote in his order. “NPS’s focus remains independent from Alliance Plaintiffs’ claims in this matter.”
Alliance for the Wild Rockies said the court decision was “a great step in the right direction.”
“There is no scientific dispute here, the bison management plan is based on outdated assumptions that thousands of bison need to be slaughtered to stop brucellosis infections in cattle,” the group said. “This is no longer accepted science and the government needs to change its management practices to keep up and base its decisions on the best available science.”
Federal agencies generally do not comment on pending litigation.
The consolidated lawsuits will continue to move forward while the agency continues its SEIS review.
Case background
The state of Montana filed suit against the federal government in late 2024, challenging the NPS’ Interagency Bison Management Plan (IBMP). The Alliance for the Wild Rockies and Council on Fish and Wildlife later filed a separate suit against the feds in early 2025. The two cases were consolidated in September 2025.
NPS said the plan would allow the agency to manage bison based on “new scientific information and circumstances that have changed since the previous EIS, completed in 2000.”
This included new scientific information about bison and brucellosis transmission, along with fewer cattle near the park, brucellosis regulations and Tribal hunting. The plan would increase the number of bison in and around the park from 3,000 head to 3,500-6,000 head and allow greater tolerance for bison outside the park boundaries.
“The decision continues the original purpose of the IBMP to maintain a wild, free ranging bison population and reduce the risk of brucellosis transmission from bison to cattle,” the agency said.
The Alliance for the Wild Rockies has contended that wild elk, not wild bison, transmit brucellosis to livestock. As part of their suit against NPS, the group alleged that the agency failed to follow recommendations from the National Academies of Science, Medicine, and Engineering to switch the focus from bison to elk for brucellosis management.
“Therefore we had to sue because no one else would hold the federal government’s feet to the fire,” the group said.
The state of Montana took issue with the feds’ alleged failure to consult the state on the plan.
“The National Park Service has repeatedly and consistently failed to engage with the State in a meaningful and transparent manner as required by law throughout the planning process,” Gov. Greg Gianforte (R) said at the time of the state’s original filing. “NPS has not given us a fair shake and has ignored concerns raised by the State. We will always defend our state from federal overreach.”
The state said the 2024 IBMP creates harm to Yellowstone National Park vegetation and range resources by increasing bison numbers, according to court documents.
The Montana Stockgrowers Association (MSGA) has questioned the 2024 plan since the scoping process began.
“MSGA continues to express its concerns with the increase in the bison population as it is likely to increase bison migration out the park and the risk of brucellosis transmission to cattle and the limited forage availability in the park during winter for a growing herd size,” MSGA Executive Vice President Raylee Honeycutt said in an October 2023 press release. — Anna Miller Fortozo, WLJ managing editor
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