This chapter does not prohibit the sale of any endangered species or threatened species, or any part or product thereof, when the owner can demonstrate that the species, or part or product thereof, was in the person’s possession before the date upon which the commission listed the species as an endangered species or threatened species or as an endangered animal or rare animal prior to January 1, 1985, and shall not prohibit the sale of that part or product by an individual not normally engaged in that sale if it was originally possessed by the seller for the seller’s own use and so used by that seller. However, it shall be unlawful to sell any species, or part or product thereof, if that sale would have been unlawful prior to the date upon which the commission added the species to the listing of endangered species or threatened species or to the listing of endangered animals or rare animals prior to January 1, 1985.