18 U.S. Code § 1716D. Nonmailable injurious animals, plant pests, plants, and illegally taken fish, wildlife, and plants

A person who knowingly deposits for mailing or delivery, or knowingly causes to be delivered by mail, according to the direction thereon, or at any place at which it is directed to be delivered by the person to whom it is addressed, anything that section 3015 of title 39 declares to be nonmailable matter shall be fined under this title, imprisoned not more than 1 year, or both.