law: Constitution of India, 1949 
     20. Protection in respect of conviction for
  
  offences.- 
  (1) No person shall be convicted of any
  
  offence except for violation of the law in force at the time of the commission
  
  of the act charged as an offence, nor be subjected to a penalty greater than
  
  that which might have been inflicted under the law in force at the time of the
  
  commission of the offence.
  (2) No person shall be prosecuted and punished
  
  for the same offence more than once.
  (3) No person accused of any offence shall be
  
  compelled to be a witness against himself.