No person in the city shall engage in any affray or assembly for any unlawful purpose, nor shall any persons gather together and conduct themselves in a disorderly, boisterous, riotous or threatening manner and a refusal of any persons so gathered together to disperse when commanded to do so by any magistrate, peace officer or any police officer, shall subject the person to the penalties prescribed by this chapter.
(`90 Code, § 14-52)