US - Importation - Mailing of Injurious Article
Summary: All kinds of poison, all articles and compositions containing poison, all poisonous animals, insects, reptiles, all explosives, inflammable materials, infernal machines, and mechanical, chemical, or other devices or compositions which may ignite or explode, all disease germs or scabs, and all other natural or artificial articles, compositions, or material which may kill or injure another, or injure the mails or other property, whether or not sealed as first-class matter, are nonmailable matter and shall not be conveyed in the mails or delivered from any post office or station thereof, nor by any officer or employee of the Postal Service.