The argument continues a Bush-era interpretation of the state of polar bears, which are at risk because of global warming.
In court papers filed Wednesday, the U.S. Fish and Wildlife Service says the animal isn't endangered under federal law.
The agency reaffirmed a 2008 decision by the Bush administration, which said the bears were threatened because of the rapid disappearance of the Arctic sea ice. The decision stopped short of declaring the bears endangered, a move that would increase protections and make oil and gas exploration more difficult.
Kassie Siegel, a lawyer for an environmental group, called the decision "a lump of coal for the polar bear."