(1) Where an offence under this Act had been committed by any person while subject to this Act, and he has ceased to be so subject, he may be taken into and kept in Security Guard custody and tried and punished for such offence as if he continued to be so subject.
     (2) No such person shall be tried for an offence, unless his trial commences within six months after he had ceased to be subject to this Act;
     Provided that nothing contained in this sub-section shall apply to the trial of any such person for an offence of desertion or for any of the offences mentioned in section 17 or shall affect the jurisdiction of a criminal court to try any offence triable by such Court as well as by a Security Guard Court.