Every license granted under the provisions hereof shall at all times be subject to the provisions of this code existing when the same shall be issued, or which shall thereafter be passed, so far as the same shall apply. And the Mayor may, in his discretion, refuse to grant any such license when he has reasonable cause to believe that the giving of any such proposed exhibition would be a violation of any provisions of this code, or he may revoke the same after having granted, for the same reasons.
('71 Code, § 4-2-3)