Except as permitted under the provisions of this Act, no person, firm or corporation shall own, possess, sell, offer for sale or transport any firearm of the kind commonly known as a machine gun or any shell cartridge or bomb containing or capable of emitting tear gas or any other noxious gas. Provided, however, that nothing in this Act contained shall prohibit the sale to, purchase by, or possession of such firearms by any city and county, county, territorial or federal officer where such firearms are required for professional use in the discharge of his duties, nor to the transportation of such firearms for or on behalf of police departments and members thereof, sheriffs, or the military or naval forces of this Territory or of the United States and “Provided, further that nothing in this Act shall prohibit police departments and members thereof, sheriffs, or the military or naval forces of the territory or of the United States from possessing or transporting such shells, cartridges or bombs for professional use in the discharge of their duties. “The term ‘shell, cartridge or bomb’, as used in this Act shall be construed to apply to and include all shells, cartridges, or bombs capable of being discharged or exploded through or by the use of percussion caps, fuses, electricity, or otherwise, when such discharge or explosion will cause or permit the release or emission of tear gases. The term ‘machine gun’ as used in this Act shall be construed to apply to and include machine rifles, machine guns and submachine guns capable of automatically and continuously discharging loaded ammunition of any caliber in which the ammunition is fed to such guns from or by means of clips, disks, drums, belts or other separable mechanical device.”