Whenever an executive or administrative function is by law or ordinance of the common council required to be performed, the same shall be performed by the proper executive or administrative officer or department, designated in the law or ordinance, and in case no such designation be thus made the mayor shall make the same, but no ordinance shall be passed interfering with the exercise of the executive functions of the officers, departments and boards of the city, as provided in this chapter or otherwise by law.
New York Legal Code