law: Indian Post Office Act, 1898 
  22. Power to postpone dispatch or delivery of certain
  
  postal articles
  (1) Where the dispatch
  
  or delivery from a post office of letters would be delayed by the dispatch or
  
  delivery there from at the same time of book, pattern or sample packets and
  
  parcels, or any of them, such packets or parcels, or any of them, may, subject
  
  to such rules as the Central Government may make in this behalf, be detained in
  
  the Post Office so long as may be necessary.
  (2) Where separate
  
  parcel posts are established, parcels may be forwarded and conveyed by them,
  
  being detained, if necessary, in the Post Office for that purpose.