A lawyer arguing for the state of Alaska that polar bears are not a threatened species ran into skeptical appeals court judges Friday.

Alaska, along with hunting groups and others, is appealing the 2011 decision by a federal judge that the government correctly listed polar bears under the federal Endangered Species Act. It’s a case with major implications because polar bears are the first, and so far only, species listed solely on the basis of threats from global warming.

Polar bears are not today on the brink. But the U.S. Fish and Wildlife Service says sea ice melting means two-thirds of the world’s polar bears could be gone by 2050.