U.S. District Judge Paul Friedman in Washington sided with environmental groups that accused the government of misreading the law last year when it lifted protections for about 4,000 wolves in Michigan, Minnesota and Wisconsin.
It was the second setback in a week for the administration's campaign to return management authority to state officials in the two regions where the wolf has rebounded after being driven to the brink of extinction in the lower 48 states.
The U.S. Fish and Wildlife Service on Sept. 23 asked a judge in Montana to return gray wolves in the Northern Rockies to the endangered list, reversing a proposal to drop them earlier this year. That followed the judge's order in July barring plans for public wolf hunts in Montana, Idaho and Wyoming.
"The Bush administration's repeated attempts to push the limits of the Endangered Species Act have been decidedly rejected by the courts," said Amy Atwood, an attorney with the Center for Biological Diversity.
The biggest practical effect of Friedman's ruling is to nullify newly established state policies allowing people in the Great Lakes area to kill wolves attacking livestock or pets. It also bars the states from permitting hunting or trapping of wolves, although none had done so.
"In our judgment, this is an animal that deserves protection," said Howard Goldman, central states regional director for The Humane Society of the United States. "It has taken so long for their numbers to recover, we've got to be very careful before removing any protections from them."
Jason Holm, spokesman for the Fish and Wildlife Service, said its attorneys were studying the ruling to determine the next step.
"We are disappointed," he said. "The service and our partners worked toward recovery of the gray wolf in the western Great Lakes for more than three decades" and considered the population "robust enough that it no longer needed Endangered Species Act protection."
The wolf occupies only about 5 percent of its historical range, which once took in most of the continental U.S.
But the animal has recovered steadily in the western Great Lakes region since the late 1970s, migrating from Minnesota into Wisconsin and Michigan's Upper Peninsula. Surveys this year turned up 2,921 wolves in Minnesota, at least 537 in Wisconsin and 520 in Michigan.
In a lawsuit challenging the Fish and Wildlife Service's 2007 decision, The Humane Society and several other groups claimed the government had acted illegally by designating Great Lakes wolves as a "distinct population segment" that could be bumped from the endangered list without regard to the species' nationwide standing.
Friedman said it was unclear whether the 1973 Endangered Species Act permits such a move. He ordered the agency to provide a better explanation of its interpretation and respond to concerns that its policy could undermine the goal of protecting the wolf. In the meantime, he returned the wolf to the federal endangered list.
"Little confusion or inefficiency will result from reinstating a regulatory regime that was in place from 1978 to 2007, particularly given the fact that state and federal wolf management authorities have been working in tandem for years," the judge said in his opinion.
But wildlife officials in the three states said the ruling would be disruptive.
"A lot of things are unknown right now," said Brian Roell, wolf coordinator for the Michigan Department of Natural Resources. "This really takes away our ability to implement our management plan."
Wisconsin will revoke permits it had issued to seven farmers allowing them to shoot wolves attacking livestock, natural resources spokeswoman Laurel Steffes said.
Until the lawsuit is resolved, state officials said they probably would seek federal permits allowing non-lethal methods to deal with wolves that continually harass livestock.
"We hope it can be resolved and we can get an answer from the Fish and Wildlife Service about what the next steps will be," said Dan Stark, spokesman for the Minnesota Department of Natural Resources.