4 U.S.C. § 8 : US Code - Section 8: Respect for flag

      No disrespect should be shown to the flag of the United States of
    America; the flag should not be dipped to any person or thing.
    Regimental colors, State flags, and organization or institutional
    flags are to be dipped as a mark of honor.
      (a) The flag should never be displayed with the union down,
    except as a signal of dire distress in instances of extreme danger
    to life or property.
      (b) The flag should never touch anything beneath it, such as the
    ground, the floor, water, or merchandise.
      (c) The flag should never be carried flat or horizontally, but
    always aloft and free.
      (d) The flag should never be used as wearing apparel, bedding, or
    drapery. It should never be festooned, drawn back, nor up, in
    folds, but always allowed to fall free. Bunting of blue, white, and
    red, always arranged with the blue above, the white in the middle,
    and the red below, should be used for covering a speaker's desk,
    draping the front of the platform, and for decoration in general.
      (e) The flag should never be fastened, displayed, used, or stored
    in such a manner as to permit it to be easily torn, soiled, or
    damaged in any way.
      (f) The flag should never be used as a covering for a ceiling.
      (g) The flag should never have placed upon it, nor on any part of
    it, nor attached to it any mark, insignia, letter, word, figure,
    design, picture, or drawing of any nature.
      (h) The flag should never be used as a receptacle for receiving,
    holding, carrying, or delivering anything.
      (i) The flag should never be used for advertising purposes in any
    manner whatsoever. It should not be embroidered on such articles as
    cushions or handkerchiefs and the like, printed or otherwise
    impressed on paper napkins or boxes or anything that is designed
    for temporary use and discard. Advertising signs should not be
    fastened to a staff or halyard from which the flag is flown.
      (j) No part of the flag should ever be used as a costume or
    athletic uniform. However, a flag patch may be affixed to the
    uniform of military personnel, firemen, policemen, and members of
    patriotic organizations. The flag represents a living country and
    is itself considered a living thing. Therefore, the lapel flag pin
    being a replica, should be worn on the left lapel near the heart.
      (k) The flag, when it is in such condition that it is no longer a
    fitting emblem for display, should be destroyed in a dignified way,
    preferably by burning.