Interior Secretary Dirk Kempthorne on May 14 announced the listing.
He said sea ice habitat has dramatically melted and computer models suggest the trend will continue.
Gov. Sarah Palin contends the decision is not based on the best scientific and commercial data.
Palin claims the federal analysis did not adequately consider polar bear survival through earlier warming periods.
She also says Kempthorne did not adequately consider existing regulatory mechanisms that have resulted in a sustainable worldwide polar bear population.