Without limiting the inherent powers of the Mayor, members of the Police Department shall be subject to disciplinary action for violation of any of the following rules and conduct:
(a) For intoxication while on duty or while in uniform.
(b) For using intoxicating liquor at any time to excess, either on or off duty.
(c) For wilful disobedience of any order lawfully issued to him by the Mayor or Acting Mayor.
(d) For incompetency to perform the duties of his office.
(e) For conviction of any crime or misdemeanor.
(f) For conduct amounting to gross neglect of duty.
(g) For conduct subversive to the good order and discipline of the Police Department.