United States Code Title 4 Chapter 1 — The Flag
§3. Use of flag for advertising purposes; mutilation of flag
Any person who, within the District of Columbia, in any manner, for exhibition or display, shall place or cause to be placed any word, figure, mark, picture, design, drawing, or any advertisement of any nature upon any flag, standard, colors, or ensign of the United States of America; or shall expose or cause to be exposed to public view any such flag, standard, colors, or ensign upon which shall have been printed, painted, or otherwise placed, or to which shall be attached, appended, affixed, or annexed any word, figure, mark, picture, design, or drawing, or any advertisement of any nature; or who, within the District of Columbia, shall manufacture, sell, expose for sale, or to public view, or give away or have in possession for sale, or to be given away or for use for any purpose, any article or substance being an article of merchandise, or a receptacle for merchandise or article or thing for carrying or transporting merchandise, upon which shall have been printed, painted, attached, or otherwise placed a representation of any such flag, standard, colors, or ensign, to advertise, call attention to, decorate, mark, or distinguish the article or substance on which so placed shall be deemed guilty of a misdemeanor and shall be punished by a fine not exceeding $100 or by imprisonment for not more than thirty days, or both, in the discretion of the court.
Put simply: Hey– you– have some respect for the FLAG and do not WALK ON IT.
Oh well, at least he stopped autographing flags.