law: Citizenship Act, 1955 
  5. Citizenship by registration 
  (1) Subject to the provisions of this section and such
  
  conditions and restrictions as may be prescribed, the prescribed authority may,
  
  on application made in this behalf, register as a citizen of India any person
  
  who is not already such citizen by virtue of the Constitution or by virtue of
  
  any of the other provisions of this Act and belongs to any of the following
  
  categories,- 
  (a) persons of Indian origin who are
  
  ordinarily resident in India and have been resident for five years immediately
  
  before making an application for registration;
  (b) persons of Indian origin who are
  
  ordinarily resident in any country or place outside undivided India;
  (c) persons who are, or have been, married to
  
  citizens of India and are ordinarily resident in India and have been so
  
  resident for five years immediately before making an application for
  
  registration.
  (d) minor children of persons who are citizens
  
  of India; and
  (e) persons of full age and capacity who are
  
  citizens of a country specified in Schedule I:
  PROVIDED  that in prescribing the conditions and
  
  restrictions subject to which persons of any such country may be registered as citizens
  
  of India under this clause, the Central Government shall have due regard to the
  
  conditions subject to which citizens of India may, by law or practice of that
  
  country, become citizens of that country by registration.
   Explanation  :  For the purposes of this sub-section,
  
  a person shall be deemed to be of Indian origin if he, or either of his
  
  parents, was born in undivided India.
  (2) No person being of full age shall be registered as a citizen
  
  of India under sub-section (1) until he has taken the oath of allegiance in the
  
  form specified in Schedule II.
  (3) No person who has renounced, or has been deprived of his,
  
  Indian citizenship, or whose Indian citizenship has terminated, under this Act
  
  shall be registered as a citizen of India under sub-section (1) except by order
  
  of the Central Government.
  (4) The Central Government may, if satisfied that there are
  
  special circumstances justifying such registration, cause any minor to be
  
  registered as a citizen of India.
  (5) A person registered under this section shall be a citizen of
  
  India by registration as from the date on which he is so registered; and a
  
  person registered under the provisions of clause (b)(ii) of Article 6 or
  
  Article 8 of the Constitution shall be deemed to be a citizen of India by
  
  registration as from the commencement of the Constitution or the date on which
  
  he was so registered, whichever may be later.