law: Trade Marks Act, 1999  
  31. Registration to be prima facie evidence of
  
  validity.- 
  (I) In all legal proceedings relating to a
  
  trade mark registered under this Act (including applications under section 57),
  
  the original registration of the trade mark and of all subsequent assignments
  
  and transmissions of the trade mark shall be prima facie evidence of the
  
  validity thereof.
  (2) In all legal proceeding as aforesaid a
  
  registered trade mark shall not be held to be invalid on the ground that it was
  
  not a registrable trade mark under section 9 except upon evidence of
  
  distinctiveness and that such evidence was not submitted to the Registrar
  
  before registration, if it is proved that the trade mark had been so used by
  
  the registered proprietor or his predecessor in title as to have become
  
  distinctive at the date of registration.