Article 9 of CoI : Article 9: Persons voluntarily acquiring citizenship of a foreign State not to be citizens.

Explanation using Example

Example 1:

Ravi was born in India and has lived in India all his life. He was a citizen of India by virtue of Article 5 of the Constitution of India. However, Ravi decided to move to Canada for better job opportunities and voluntarily acquired Canadian citizenship. According to Article 9 of the Constitution of India, Ravi will no longer be considered a citizen of India because he has voluntarily acquired the citizenship of a foreign state.

Example 2:

Priya was born in India and her parents were Indian citizens. She moved to the United States for higher education and eventually decided to settle there. Priya applied for and obtained U.S. citizenship. Despite her Indian origin and the fact that she was an Indian citizen by virtue of Article 6, Priya will lose her Indian citizenship as per Article 9 of the Constitution of India because she voluntarily acquired U.S. citizenship.