Three 9th Circuit Court of Appeals justices upheld U.S. District Judge Donald Molloy’s 2010 order to return grizzly bears in the greater Yellowstone ecosystem to the threatened species list.

The court ruled that the disappearance of whitebark pine, a key food source, threatens bears’ long-term survival.

The federal government, Idaho, Montana and Wyoming argued the bears won’t go extinct if states are left to manage them. But the judges said federal managers were too aggressive about delisting the population that stands at about 600 bears.

U.S. Fish and Wildlife Service Grizzly Bear Coordinator Chris Servheen said the court ruled the agencies’ conservation strategy is an adequate regulatory mechanism to protect the bear after delisting. That gives the federal government and the states a chance to rework the rule and bring it back to the public again.

“We have to do a better job of explaining why the loss of whitebark pine is not something that would inhibit the recovery of Yellowstone grizzly bears,” Servheen said.

But Louisa Willcox, a bear advocate for the Natural Resources Defense Council, said federal officials should bring climatologists and whitebark pine experts into the process before trying to delist. She also wants them to listen to groups like hers, hunters and ranchers and seek new ways to reduce conflicts.

“This should be a clarion call to regroup and redo how the recovery process works,” Willcox said.