law: Citizenship Act, 1955 
  7. Citizenship by incorporation of territory 
  (1) If any territory becomes a part of India, the Central
  
  Government may, by order notified in the Official Gazette, specify the persons
  
  who shall be citizens of India by reason of their connection with that
  
  territory; and those persons shall be citizens of India as from the date to be
  
  specified in the order.