18 U.S.C. § 1461: Mailing obscene or crime-inciting matter

Every obscene, lewd, lascivious, indecent, filthy or vile article, matter, thing, device, or substance; and— Every article or thing designed, adapted, or intended for producing abortion, or for any indecent or immoral use; and Every article, instrument, substance, drug, medicine, or thing which is advertised or described in a manner calculated to lead another to use or apply it for producing abortion, or for any indecent or immoral purpose; and Every written or printed card, letter, circular, book, pamphlet, advertisement, or notice of any kind giving information, directly or indirectly, where, or how, or from whom, or by what means any of such mentioned matters, articles, or things may be obtained or made, or where or by whom any act or operation of any kind for the procuring or producing of abortion will be done or performed, or how or by what means abortion may be produced, whether sealed or unsealed; and Every paper, writing, advertisement, or representation that any article, instrument, substance, drug, medicine, or thing may, or can, be used or applied for producing abortion, or for any indecent or immoral purpose; and Every description calculated to induce or incite a person to so use or apply any such article, instrument, substance, drug, medicine, or thing— Is declared to be nonmailable matter and shall not be conveyed in the mails or delivered from any post office or by any letter carrier. Whoever knowingly uses the mails for the mailing, carriage in the mails, or delivery of anything declared by this section or section 3001(e) of title 39 to be nonmailable, or knowingly causes to be delivered by mail according to the direction thereon, or at the place at which it is directed to be delivered by the person to whom it is addressed, or knowingly takes any such thing from the mails for the purpose of circulating or disposing thereof, or of aiding in the circulation or disposition thereof, shall be fined under this title or imprisoned not more than five years, or both, for the first such offense, and shall be fined under this title or imprisoned not more than ten years, or both, for each such offense thereafter. The term “indecent”, as used in this section includes matter of a character tending to incite arson, murder, or assassination.