The term "Article 9" most commonly refers to a provision in Part II (Citizenship) of the Constitution of India, though an informed reader should also know the famous "No War" clause in the Constitution of Japan and the right against arbitrary detention in the Universal Declaration of Human Rights (UDHR).
Article 9 of the Indian Constitution is a provision that establishes the principle of single allegiance by barring dual citizenship. It was debated in the Constituent Assembly on August 10, 11, and 12, 1949, and was created to ensure that Indian nationality is based on loyalty to the Indian State alone. The mechanism is straightforward: the provision states that "No person shall be a citizen of India by virtue of article 5, or be deemed to be a citizen of India by virtue of article 6 or article 8, if he has voluntarily acquired the citizenship of any foreign State."
This means that if an Indian citizen voluntarily obtains the citizenship of another country, their Indian citizenship is automatically terminated. Article 9 is a cornerstone of the constitutional framework for citizenship, which is laid out in Articles 5 to 11 of the Constitution. The statutory law connected to this provision is the Citizenship Act, 1955, which was enacted by Parliament under the power granted by Article 11 and includes Section 9 to deal with the termination of citizenship upon voluntary acquisition of a foreign nationality. The core principle of barring dual citizenship under Article 9 has remained unchanged since the Constitution's commencement.