Environmental activists are trying to restrict hunting opportunities on federal public lands.

On Monday, a non-profit environmental advocacy organization filed suit against the U.S. Fish and Wildlife Service in a Montana federal court. The lawsuit alleges that the agency is failing to protect vulnerable and endangered species by allowing hunting on National Wildlife Refuge land. The group claimed lead ammunition could harm protected wildlife even if they aren’t directly shot with it.

“The Center for Biological Diversity brings this lawsuit to challenge a rule heralded by the Trump Administration as the largest-ever expansion of hunting and fishing on the National Wildlife Refuge System,” the suit said. “Promulgated by U.S. Fish and Wildlife Service, the Hunting and Fishing Rule expands use of lead ammunition and tackle on numerous units of the Refuge System, including refuges where the agency never previously allowed hunting or fishing.”

The suit takes direct aim at a rule finalized in August of 2020 that marked the culmination of the Trump administration’s efforts to increase access to public lands for outdoor sporting and recreation. If the lawsuit is successful, up to 2.3 million acres of federal public land across the country could be made off-limits for hunting, sport shooting, and fishing.

At the time the rule was enacted, the Department of the Interior called it the single largest expansion of hunting and fishing opportunities in the Fish and Wildlife Service’s history. But environmental advocates say that expansion could come at a cost to threatened, non-game species.

“Opening national refuges to increased hunting means that rare and beautiful animals like grizzly bears, ocelots and whooping cranes now face increased risk of death, ingestion of toxic lead shot, and other harms,” Camila Cossio, an attorney for the Center for Biological Diversity, said. “With wildlife already confronted by so many threats to their survival, they rely on refuges to be safe havens.”

The National Wildlife Refuge System currently consists of 567 refuges with a purpose distinct from other types of public lands. According to the Fish and Wildlife Service website, “Wildlife conservation drives everything on national wildlife refuges, from the purposes for which each refuge was established, to the recreational activities offered, to the resource management tools used.”

However, the plaintiffs in the case see the agency as failing to live up to that mission.

“We’re going to court to ensure that our nation’s wildlife refuges actually provide refuge to endangered wildlife,” Cossio said. “The Fish and Wildlife Service is shrugging off the many risks that sport hunting and fishing pose to endangered animals, particularly from lead ammunition and tackle.”

Spokespersons for the Fish and Wildlife Service did not respond to a request for comment. However, the agency’s website says allowing hunting on refuge land can play a valuable role in conservation.

“As practiced on refuges, hunting does not pose a threat to the wildlife populations – and in some instances it is necessary for sound wildlife management,” the site says. “The harvesting of wildlife on refuges is carefully regulated to ensure equilibrium between population levels and wildlife habitat.”