law: Advocates Act, 1961
  Chapter III
  16. Senior and other
  
  advocates,--
  (1) there shall be two
  
  classes of advocates, namely , senior advocates and other advocates.
  (2) An advocate may, with his consent, be designated as senior
  
  advocate if the Supreme Court or a High Court is of opinion that by virtue of
  
  his ability[ standing at the Bar or special knowledge or experience in law] he
  
  is deserving of such distinction.
  (3) Senior advocates, shall in the matter of their practice, be
  
  subject to such restrictions as the Bar Council of India may, in the interest
  
  of the legal profession, prescribe.
  (4) An advocate of the Supreme Court who was senior advocate of
  
  that Court immediately before the appointed day shall, for the purposes of this
  
  section, be deemed to be a senior advocate ;
  [ (Note:- Added by Act 21 of 1964, sec.8)  Provided that
  
  where any such senior advocate makes an application before the 31st
  
  December, 1965, to the Bar council maintaining the roll in which his name has
  
  been entered that he does not desire to continue as a senior advocate, the Bar
  
  Council may grant the application and the roll shall be altered accordingly].