Environmental groups asked a federal judge Thursday to put gray wolves back on the endangered species list in the Northern Rockies.
Two lawsuits were filed in federal court in Montana as control over more than 1,300 wolves was turned over to state authorities in Montana, Idaho, Oregon, Washington and Utah.
A federal budget bill rider in April had mandated Thursday's lifting of wolf protections.
Western lawmakers who backed the measure said they wanted to circumvent U.S. District Judge Donald Molloy, who blocked prior efforts to lift protections and allow hunting.
But environmentalists say that because the case before Molloy was pending, Congress violated the separation of powers doctrine outlined in the Constitution that bars interference with the judiciary.
"They were playing judge rather than legislators and they can't do that," said Michael Garrity of the Alliance for the Wild Rockies, which joined Friends of the Clearwater and WildEarth Guardians in one of the lawsuits.
The plaintiff in the other case is the Center for Biological Diversity.
After being driven to near-extinction in the past century, wolves have bounced back dramatically in the decades since being placed on the endangered list. Biologists say the species is fully recovered but environmentalists worry overhunting will harm the population.
Public wolf hunts are planned this fall in Montana and Idaho.
Montana Fish Wildlife and Parks spokesman Ron Aasheim said a final decision is due July 14 on a proposal to allow 220 wolves to be killed. Idaho has not yet proposed a wolf hunt quota for 2011.