Parades and demonstrations held pursuant to a permit issued under the provisions of this subchapter which become, or which reasonably appear to present an imminent threat to becoming, a riot, rout or unlawful assembly shall be dispersed forthwith by the city police or by any law enforcement officer who may be present. Persons who are commanded to disperse by any law enforcement officer shall promptly obey such command and peacefully disengage themselves from such parade or demonstration and leave the scene thereof, and persons who fail to obey such command shall be subject to immediate arrest. (Prior Code, § 315.12)