18 U.S.C. § 712: Misuse of names, words, emblems, or insignia

Whoever, in the course of collecting or aiding in the collection of private debts or obligations, or being engaged in furnishing private police, investigation, or other private detective services, uses or employs in any communication, correspondence, notice, advertisement, or circular the words “national”, “Federal”, or “United States”, the initials “U.S.”, or any emblem, insignia, or name, for the purpose of conveying and in a manner reasonably calculated to convey the false impression that such communication is from a department, agency, bureau, or instrumentality of the United States or in any manner represents the United States, shall be fined under this title or imprisoned not more than one year, or both.