A federal judge Thursday overturned the Interior Department's decision to remove Endangered Species Act protections for the gray wolf in some parts of the Northern Rocky Mountains -- but not all -- saying the government couldn't pick and choose which wolves to delist and which not to.

The ruling by U.S. District Judge Donald Molloy in Montana -- heralded by conservation groups that have maintained that a sound wolf recovery program couldn't sustain itself, genetically, without two or three times the estimated 1,500 or so wolves loping about Montana, Idaho, and Wyoming -- surely will infuriate some groups that see wolves as nothing more than four-legged killing machines.

The bottom line under the 50-page ruling is that U.S. Fish and Wildlife Service erred when it decided that gray wolves in Wyoming should retain ESA protection, while wolves in Idaho and Montana could be delisted. As a result, wolves in all three states will regain ESA protection, a move that -- if it stands -- will bring an end to their legal hunting in Montana and Idaho.

Key to the ruling were the judge's findings that:

The Endangered Species Act does not allow the U.S. Fish & Wildlife Service to list only part of a "species" as endangered, or to protect a listed distinct population segment only in part as the Final Rule here does; and the legislative history of the Endangered Species Act does not support the Service's new interpretation of the phrase "significant portion of its range." To the contrary it supports the historical view that the Service has always held, the Endangered Species Act does not allow a distinct population segment to be subdivided.

"Accordingly," Judge Molloy continued, "the rule delisting the gray wolf must be set aside because, though it may be a pragmatic solution to a difficult biological issue, it is not a legal one."

Interior Secretary Ken Salazar in March 2009 upheld a decision by the Fish and Wildlife Service to remove ESA protection from thousands of gray wolves, including many in the Greater Yellowstone Ecosystem. At the time, the Fish and Wildlife Service had decided to delist the wolf in Idaho and Montana because those states have approved wolf management plans in place that will ensure the conservation of the species in the future. At the same time, the agency determined wolves in Wyoming would still be listed under the Act because Wyoming’s current state law and wolf management plan were not sufficient to conserve its portion of northern Rocky Mountain wolf population.

In announcing his decision, Secretary Salazar called the wolf recovery program that was launched in Yellowstone National Park back in 1995 a resounding success.

“The recovery of the gray wolf throughout significant portions of its historic range is one of the great success stories of the Endangered Species Act,” the secretary said at the time. “When it was listed as endangered in 1974, the wolf had almost disappeared from the continental United States. Today, we have more than 5,500 wolves, including more than 1,600 in the Rockies.

“The successful recovery of this species is a stunning example of how the Act can work to keep imperiled animals from sliding into extinction,” he added. “The recovery of the wolf has not been the work of the federal government alone. It has been a long and active partnership including states, tribes, landowners, academic researchers, sportsmen and other conservation groups, the Canadian government and many other partners.”

But in rejecting many of the government's arguments and its decision that the wolf could have Endangered Species Act protection in some parts of the Rockies -- Wyoming -- but not in others -- Idaho and Montana --, the judge said Congress was quite clear when it passed the act that "a species must be protected if it faces worldwide extinction, or something less than that."

"The listing depends on when a species is endangered in all or in a significant portion of its range. Defendants' reasoning is like saying an orange is an orange only when it is hanging on a tree," wrote Judge Molloy.

At the Natural Resources Defense Council's Montana offices, Matt Skoglund applauded the ruling.

"We’re relieved to see Endangered Species Act protections returned to all wolves in the Northern Rockies. It’s now time to reopen the recovery plan, update the science and recovery standards, and come up with a plan that ensures the recovery of wolves in the Northern Rockies over the long term," said Mr. Skoglund. "The Northern Rockies were wolf-less mountains for most of the 20th century, and we want to see their remarkable recovery since the mid-‘90s continue. With this ruling today, it’s clearly time to take a fresh look at the long-term recovery plan for Northern Rockies wolves."