18 U.S.C. § 912 : US Code - Section 912: Officer or employee of the United States

      Whoever falsely assumes or pretends to be an officer or employee
    acting under the authority of the United States or any department,
    agency or officer thereof, and acts as such, or in such pretended
    character demands or obtains any money, paper, document, or thing
    of value, shall be fined under this title or imprisoned not more
    than three years, or both.