Gray wolves in the northern Rocky Mountains were reintroduced on the list of endangered species on Friday after a federal judge in Montana addressed a formal command to environmentalists, who had proposed the removal of the animals' official protection.

However, the measures taken by Judge Donald W. Molloy of Federal District Court came only as a preliminary injunction and are not necessarily permanent. Nevertheless, Judge Molloy showed strong doubts regarding the Fish and Wildlife Service's decision announced in February this year. The agency decided to cut the gray wolves off the endangered species list after meeting the goals they had proposed. After an almost 20-year effort, the target was reached. Environmentalists managed to reestablish the wild animals in Idaho, Montana and Wyoming.

Molloy stated in a 40-page order released on Friday night that the conclusion of the Fish and Wildlife Service seriously jeopardized the expansion of the species.

The injunction will "ensure the species is not imperiled," restoring endangered species protection while the case continues to be assessed, according to the judge.

However, his order will also put in motion a federal rule that was changed in January in order to permit the animals to be killed if they endangered any property. Thus, the rule authorizes ranchers to shoot wolves when they consider they are threatened.

Doug Honnold, the lawyer for Earthjustice, declared in an e-mail message to the New York Times that it was a brand new start for wolves. “All three states had plans to allow hunts this fall, 500 wolves were scheduled to be killed”, he said.

The topic regarding wolves has been the subject of harsh debates since they were brought again to Yellowstone National Park in 1995.