law: 31. Punishment for second and subsequent offences.-
  If any person convicted of an offence under sub-section (1) of section 26 or section 27 or section 29 or section 30 is again convicted for an offence under any of the aforesaid provisions, he shall be punishable for the second and for every subsequent offence with rigorous imprisonment for a term which shall not be less than six months but which may extend to seven years and with fine.