Article 5 of Constitution of India "Citizenship at the commencement of the Constitution"
At the commencement of this Constitution every person who
has his domicile in the territory of India and -
(a) who was born in the territory of India; or
(b) either of whose parents was born in the territory of
India; or
(c) who has been ordinarily resident in the territory of
India for not less than five years preceding such
commencement, shall be a citizen of India
Article 6 of Constitution of India "Citizenship at the commencement of the Constitution"
Notwithstanding anything in Article 5, a person who has
migrated to the territory of India from the territory now
included in Pakistan shall be deemed to be a citizen of
India at the commencement of this Constitution if-
(a) he or either of his parents or any of his grand-parents
was born in India as defined in the Government of India Act,
1935 (as originally enacted); and
(b) (i) in the case where such person has so migrated before
the nineteenth day of July, 1948, he has been ordinarily
resident in the territory of India since the date of his
migration, or
(ii) in the case where such person has so migrated on or
after the nineteenth day of July, 1948, he has been
registered as a citizen of India by an officer appointed in
that behalf by the Government of the Dominion of India on an
application made by him therefor to such officer before the
commencement of this Constitution in the form and manner
prescribed by that Government:
Provided that no person shall be so registered unless he has
been resident in the territory of India or at least six
months immediately preceding the date of his application.