Where the Central Government is of the opinion that it is necessary or expedient so to do, either in the public interest or having regard to the peculiar circumstances of any case, it may, by notification in the Official Gazette and subject to such conditions, if any, as it may specify in the notification,--
         (a) exempt any person or class of persons from the operation of all or any of the provisions of this Act; and
         (b) cancel any such notification and again subject, by a like notification, the person or class of persons to the operation of such provisions.