26 U.S.C. § 7621 : US Code - Section 7621: Internal revenue districts

    (a) Establishment and alteration
      The President shall establish convenient internal revenue
    districts for the purpose of administering the internal revenue
    laws. The President may from time to time alter such districts.
    (b) Boundaries
      For the purpose mentioned in subsection (a), the President may
    subdivide any State, or the District of Columbia, or may unite into
    one district two or more States.