A coalition of environmental and animal protection groups said Wednesday that it will sue to overturn the U.S. Fish and Wildlife Services decision not to restore Endangered Species Act protections for gray wolves in the Northern Rockies.

The lawsuit would mark the latest chapter in a long-running controversy over the status of gray wolves in the Republican-led states of Montana, Idaho and Wyoming, which have adopted liberal hunting and trapping seasons in an effort to reduce populations since the delisting ceded management to the states.

The state legislatures of Idaho and Montana took the unusual step of dictating wildlife management by law instead of deferring to wildlife officials and commissions, and stepped in to loosen restrictions on killing wolves in recent years.