The American Civil Liberties Union has asked Yellowstone National Park to allow public access to an area near Gardiner where captured wild bison are being held for slaughter.
An attorney for the ACLU said in a Friday letter to Yellowstone Administrator Dan Wenk that the closure of the Stephens Creek facility and surrounding areas of the park violates the public's right to observe the capture activities.
The civil liberties group represents wildlife advocates from the Buffalo Field Campaign and freelance journalist Christopher Ketcham.
Park spokeswoman Amy Bartlett says a media tour of Stephens Creek is planned in coming weeks.
More than 250 Yellowstone bison have been captured and slaughtered or removed for research purposes this winter. Officials want to reduce the population by up to 900 bison to curb the animals' winter migration into Montana.