The hearing before U.S. District Judge Donald Molloy in Missoula came as Idaho and Montana prepare for fall hunts in which hundreds of wolves could be killed. Molloy has twice blocked prior attempts to lift protections for the predators.
This time around, he is considering whether Congress violated the separation of powers under the U.S. Constitution with legislation crafted to circumvent his earlier rulings.
Congress approved a budget bill in April that contained a provision targeting. Several conservation and environmental groups filed suit in May, saying Congress crossed the divide that separates the branches of the federal government by getting involved in a pending legal case instead of sticking to its role of making law.
Government biologists say wolves reached sustainable population levels a decade ago and would likely continue to thrive in the Northern Rockies under state management.
Wolves also were taken off the endangered species list in Washington, Oregon and Utah, but no hunts are planned in those states.
Wolves in Wyoming remain on the list due to concerns among federal officials over a law allowing the predators to be shot on sight across most of the state. (AP)