No person shall place or maintain or display any device, other than an official warning or direction sign, or signal erected under competent authority upon or in view of a street which purports to be, or is in imitation of, or resemblance of an official warning or direction sign or signal, or which attempts to direct the movement of traffic or the action of operators and any such prohibitive device shall be a nuisance, and the Chief of Police may remove it without notice. (3210.19 -- Ord. 996 § 2 (part), 1959).