An application from a person, who is married to a citizen of India, for registration as a citizen of India under clause (c) of sub-section (1) of section 5 shall not be entertained unless – (a) the application is made in Form III; (b) he gives an undertaking in writing that he shall renounce the citizenship of his country in the event of his application being sanctioned; (c) on the date of making the application he,-  (i) has been ordinarily a resident of India; or  (ii) has been in the service of the Government of India;  at least for a period of seven years; and  (d) he makes the oath of allegiance as specified in the Second Schedule to the Citizenship Act, 1955. Explanation.- In computing the period of seven years, any broken period of residence and service under sub-clauses (i) and (ii) of clause (c) shall be included in the period specified therein.

Citizenship Act, 1955