BILLINGS, Mont. - A federal judge has restored endangered species protections for gray wolves in the Northern Rockies, derailing plans by three states to hold public wolf hunts this fall.

U.S. District Judge Donald Molloy in Missoula granted a preliminary injunction late Friday restoring the protections for the wolves in Montana, Wyoming and Idaho. Molloy will eventually decide whether the injunction should be permanent.

The region has an estimated 2,000 gray wolves. They were removed from the endangered species list in March, following a decade-long restoration effort.

©AP Photo/U.S. Fish & Wildlife Service, File

A gray wolf.

Environmentalists sued to overturn the decision, arguing wolf numbers would plummet if hunting were allowed. They sought the injunction in the hopes of stopping the hunts and allowing the wolf population to continue expanding.

"There were fall hunts scheduled that would call for perhaps as many as 500 wolves to be killed. We're delighted those wolves will be saved," said attorney Doug Honnold with Earthjustice, who had argued the case before Molloy on behalf of 12 environmental groups.

In his ruling, Molloy said the federal government had not met its standard for wolf recovery, including interbreeding of wolves between the three states to ensure healthy genetics.

"Genetic exchange has not taken place," Molloy wrote in the 40-page decision.

Molloy said hunting and state laws allowing the killing of wolves for livestock attacks would likely "eliminate any chance for genetic exchange to occur."

The federal biologist who led the wolf restoration program, Ed Bangs, defended the decision to delist wolves as "a very biologically sound package."

"The kind of hunting proposed by the states wouldn't threaten the wolf population," Bangs said Friday. "We felt the science was rock solid and that the delisting was warranted."

Bangs said government attorneys were reviewing Molloy's court order and would decide next week whether to appeal to the 9th U.S. Circuit Court of Appeals.

Federal and state officials had argued killing some wolves would not endanger the overall population - as long as numbers did not dip below 300 wolves. With increasing conflicts between wolves and livestock, they said public hunts were crucial to keeping the predators' population in check.