law: 158. Special provision regarding Scheduled Tribes.-
  No transfer of land by a person who is a member of the Scheduled Tribes shall be valid unless-
  (a) the transfer is to another member of the Scheduled Tribes; or
  (b) where the transfer is to a person who is not a member of any such tribe, it is made with the previous permission in writing of the deputy commissioner; or
  (c) the transfer is by way of mortgage to a co-operative society.