The greater Yellowstone area of the northern Rocky Mountains has an estimated number of 2,000 gray wolves. They all regained endangered-species protection on Friday by a judge in Montana. The new rule challenged the wolves’ delisting and didn’t permit hunters from three states to kill them.

Another law for the gray wolves was released in March, after the U.S. Fish and Wildlife officials announced in February that the wolves would be removed from the endangered species list. Their termed a successful 20-year effort to reestablish the wolves in Idaho, Montana and Wyoming, but the environmentalists sued.

A 40-page order issued in February, U.S. District Judge Donald W. Molloy of Missoula, Montana, said that the wolves’ delisting arbitrary “demonstrated a possibility of irreparable harm” to the species.

The order will also change the federal rule that was modified in January and will allow ranchers to kill the wolves if they threaten their property.

Gray wolves species ranged from central Mexico to the Arctic and by the 1930s, but the hunting wiped them out across the American West. By 1974, the gray wolves were listed as dangerous.

Officials introduced 66 wolves to central Idaho and Yellowstone National Park in 1996. The goal of bringing the wolves was to establish a stable population of at least 300 animals. Earlier this year, wolves in the northern Rockies numbered nearly 1,513. Officials of the wildlife say that the wolves’ population increases by 24% a year.