law: Citizenship Act, 1955 
  9. Termination of citizenship 
  (1) Any citizen of India who by naturalization, registration or
  
  otherwise voluntarily acquires, or has at any time between the 26th January,
  
  1950 and the commencement of this Act voluntarily acquired, the citizenship of
  
  another country shall, upon such acquisition or, as the case may be, such
  
  commencement, cease to be a citizen of India:
  PROVIDED  that nothing in this sub-section shall apply
  
  to a citizen of India who, during any war in which India may be engaged,
  
  voluntarily acquires the citizenship of another country, until the Central
  
  Government otherwise directs.
  (2) If any question arises as to whether, when or how any person
  
  has acquired the citizenship of another country, it shall be determined by such
  
  authority, in such manner, and having regard to such rules of evidence, as may
  
  be prescribed in this behalf.