84.012.  Ordinances by common council or municipal assembly, permissible — ordinances in conflict with board of police commissioners prohibited. — In all cities of this state not within a county, the common council or municipal assembly of such cities may pass ordinances for preserving order; securing property and persons from violence, danger, or destruction; protecting public and private property; and promoting the interests and ensuring the good governance of the cities, but no ordinances heretofore passed, or that may hereafter be passed, by the common council or municipal assembly of the cities shall, in any manner, conflict or interfere with the powers or the exercise of the powers of the boards of police commissioners of the cities as created by section 84.020, nor shall the cities or any officer or agent of the corporation of the cities, or the mayor thereof, in any manner impede, obstruct, hinder, or interfere with the boards of police, any officer, agent, or servant thereof or thereunder.