ANCHORAGE, Alaska – Environmental and animal rights groups are lining up to oppose a lawsuit that seeks to let American sport hunters again import hides of polar bears shot legally in Canada.

The hunting group Safari Club International has filed a notice of its intent to sue to overturn the ban, which was put in place last month when U.S. Department of Interior Secretary Dirk Kempthorne declared polar bears a threatened species.

The group seeks to overturn the ban not just for bears already killed but also for kills by club members who booked and paid for hunts in 2009 and 2010.

Supporters of the ban say sport hunting adds stress to polar bears already menaced by a loss of sea ice, their main habitat.

“Until we take steps to address global warming, we need to do all we can to relieve further threats that are accelerating the bears' downward spiral, including the trophy hunting of polar bears in Canada,” said Rodger Schlickeisen, president of Defenders of Wildlife.

Kempthorne on May 15 declared polar bears threatened, or likely to become endangered in the future, because of habitat loss.

Trophy hunting of bears in Alaska has been banned since 1972. Canada allows the sport hunting of polar bears, but it restricts the hunting season to two months and limits the number of kills.

Importation had been allowed through an amendment to the Marine Mammal Protection Act passed by Congress in 1994.

Kempthorne, however, declared polar bears threatened throughout their range, and the U.S. Fish and Wildlife Service withdrew authorization to import hides from animals killed in approved populations in Canada – including those already killed and awaiting a taxidermist mount.

Safari Club International attorney Doug Burdin said Wednesday that a listing under the Endangered Species Act does not create an import ban. The Fish and Wildlife Service did not follow the law in banning hides, he said.

“They never held any kind of rule-making for designating the polar bear as a depleted species under the Marine Mammal Protection Act,” Burdin said.

The organization might join the state of Alaska in suing to overturn the listing but so far has only filed to overturn the ban on importing hides, he said.

Politicians from Canada's Northwest Territory traveled to Washington this week to ask Interior Department officials to lift the import ban.

Bob McLeod, the Northwest Territory's minister for energy, industry and tourism, said Monday the import ban would effectively wipe out its sports hunting industry.

Safari Club International argues that income from hunters helps support polar bear research and provides an economic benefit to Canada's native communities, which provide guides and other services for hunters. A hunt can cost $40,000 to $50,000, the organization said.

Several groups want more, not fewer, protections for polar bears and plan to intervene in any lawsuit initiated by Safari Club International to overturn an import ban. Among them: the Center for Biological Diversity, the Natural Resources Defense Council and Greenpeace, which petitioned for the polar bear listing as a threatened species.

The groups point to a U.S. Geological Service study released last year that concluded Alaska's polar bears, and two of the six Canadian polar bear populations from which Americans imported polar bear trophies, could be gone by 2050 because of warming and its effect on sea ice.