The provisions of the preceding section shall not apply to officers of the law, to persons holding hunting or fishing licenses when lawfully engaged in hunting or fishing, to employees of express companies while on duty, to watchmen while on duty, to emergency medical technicians, firefighters, or military personnel while in the course of their duties, or to duly authorized military or civic organizations when parading, or to the members thereof when at, or going to or from, their customary places of assembly.