18 U.S.C. § 700 : US Code - Section 700: Desecration of the flag of the United States; penalties

      (a)(1) Whoever knowingly mutilates, defaces, physically defiles,
    burns, maintains on the floor or ground, or tramples upon any flag
    of the United States shall be fined under this title or imprisoned
    for not more than one year, or both.
      (2) This subsection does not prohibit any conduct consisting of
    the disposal of a flag when it has become worn or soiled.
      (b) As used in this section, the term "flag of the United States"
    means any flag of the United States, or any part thereof, made of
    any substance, of any size, in a form that is commonly displayed.
      (c) Nothing in this section shall be construed as indicating an
    intent on the part of Congress to deprive any State, territory,
    possession, or the Commonwealth of Puerto Rico of jurisdiction over
    any offense over which it would have jurisdiction in the absence of
    this section.
      (d)(1) An appeal may be taken directly to the Supreme Court of
    the United States from any interlocutory or final judgment, decree,
    or order issued by a United States district court ruling upon the
    constitutionality of subsection (a).
      (2) The Supreme Court shall, if it has not previously ruled on
    the question, accept jurisdiction over the appeal and advance on
    the docket and expedite to the greatest extent possible.