Polar Bear Conservation and Fairness Act of 2013 - Amends the Marine Mammal Protection Act of 1972 to direct the Secretary of the Interior to issue a permit for the importation of any polar bear part (other than an internal organ) from a polar bear taken in a sport hunt in Canada to any person who submits proof that the polar bear was legally harvested before May 15, 2008 (currently by February 18, 1997), when polar bears were listed as a threatened species by the Department of the Interior.