law: Citizenship Act, 1955 
  8. Renunciation of citizenship 
  (1) If any citizen of India of full age and capacity, who is
  
  also a citizen or national of another country, makes in the prescribed manner a
  
  declaration renouncing his Indian citizenship, the declaration shall be
  
  registered by the prescribed authority, and, upon such registration, that
  
  person shall cease to be a citizen of India:
  PROVIDED  that if any such declaration is made during
  
  any war in which India may be engaged, registration thereof shall be withheld
  
  until the Central Government otherwise directs.
  (2) Where 6[a person] ceases to be a citizen of India
  
  under sub-section (1) every minor child of that person shall thereupon cease to
  
  be a citizen of India:
  PROVIDED  that any such child may, within one year after
  
  attaining full age, make a declaration that he wishes to resume Indian
  
  citizenship and shall thereupon again become a citizen of India.