What statute says its illegal to intercept other people's mail?

Answer 1

18 U.S.C. § 1702: "Whoever takes any letter, postal card, or package out of any post office or any authorized depository for mail matter, or from any letter or mail carrier, or which has been in any post office or authorized depository, or in the custody of any letter or mail carrier, before it has been delivered to the person to whom it was directed, with design to obstruct the correspondence, or to pry into the business or secrets of another, or opens, secretes, embezzles, or destroys the same, shall be fined under this title or imprisoned not more than five years, or both." (current as of April 2, 2012). Note also, for purposes of this section a private mailbox is a "authorized depository" for mail matter, and "the statute is applicable until the mailed material is physically delivered to the person to whom it is directed or to his authorized agent." U.S. v. Ashford, 530 F.2d 792, 795-96 (8th Cir. 1976).