The commanding officer of any unit of the national guard parading or performing any military duty in any street or highway may require any or all persons in such street or highway to yield the right-of-way to said national guard; provided that the carriage of the United States mail, the legitimate functions of the police and the progress and operations of the hospital ambulances, fire engines and fire departments shall not be unduly interfered with thereby. All others who shall hinder, delay or obstruct any unit of the national guard wherever parading or performing any military duty, or who shall attempt to do so, shall be guilty of a misdemeanor.