Indian citizenship and nationality law: The Constitution of India provides for a single citizenship for the entire country. The provisions relating to citizenship at the commencement of the Constitution are contained in Articles 5 to 11 in Part II of the Constitution of India. Relevant Indian legislation is the Citizenship Act 1955, which has been amended by the Citizenship (Amendment) Act 1986, the Citizenship (Amendment) Act 1992, the Citizenship (Amendment) Act 2003, and the Citizenship (Amendment) Ordinance 2005 The Citizenship (Amendment) Act 2003 received the assent of the President of India on 7 January 2004 and came into force on 3 December 2004. The Citizenship (Amendment) Ordinance 2005 was promulgated by the President of India and came into force on 28 June 2005.
Following these reforms, Indian nationality law largely follows the jus sanguinis (citizenship by right of blood) as opposed to the jus soli (citizenship by right of birth within the territory).
Person born outside India on or after 10 December 1992 are considered as citizens of India if either of their parents is a citizen of India at the time of their birth.
From 3 December 2004 onwards, persons born outside of India shall not be considered citizens of India unless their birth is registered at an Indian consulate within one year of the date of birth. In certain circumstances it is possible to register after 1 year with the permission of the Central Government. The application for registration of the birth of a minor child must be made to an Indian consulate and must be accompanied by an undertaking in writing from the parents of such minor child that he or she does not hold the passport of another country.
Termination is covered in Section 9 of the Citizenship Act, 1955. The provisions for termination are separate and distinct from the provisions for making a declaration of renunciation.
Section 9(1) of the act provides that any citizen of India who by naturalisation or registration acquires the citizenship of another country shall cease to be a citizen of India. It also provides that any citizen of India who voluntarily acquires the citizenship of another country shall cease to be a citizen of India. Notably, the termination provision differs from the renunciation provision because it applies to "any citizen of India" and is not restricted to adults. Indian children therefore also automatically lose their claim to Indian citizenship if at any time after birth they acquire a citizenship of another country by, for example, naturalisation or registration — even if the acquisition of another citizenship was done as a result of actions by the child's parents.
The acquisition of another country's passport is also deemed under the Citizenship Rules, 1956 to be voluntary acquisition of another country’s nationality. Rule 3 of Schedule III of the Citizenship Rules, 1956 states that "the fact that a citizen of India has obtained on any date a passport from the Government of any other country shall be conclusive proof of his having voluntarily acquired the citizenship of that country before that date". Again, this rule applies even if the foreign passport was obtained for the child by his or her parents, and even if possession of such a passport is required by the laws of a foreign country which considers the child to be one of its citizens (e.g., a U.S.-born child of Indian parents who is automatically deemed to be a U.S. citizen according to U.S. law, and who is therefore required by U.S. law to have a U.S. passport in order to travel abroad). It does not matter that a person continues to hold an Indian passport. Persons who acquire another citizenship lose Indian citizenship from the date on which they acquire that citizenship or another country's passport. The prevailing practice at a number of British diplomatic posts, for example, is to impound and return to the Indian authorities the Indian passports of those applicants who apply for and are granted British passports
Special rules exist for Indian citizens with a connection to Goa, Daman and Diu. Rule 3A of Schedule III of the Citizenship Rules, 1956 states that "Where a person, who has become an Indian Citizen by virtue of the Goa, Daman and Diu (Citizenship) Order, 1962, or the Dadra and Nagar Haveli (Citizenship) Order 1962, issued under section 7 of the Citizenship Act, 1955 (57 of 1955) holds a passport issued by the Government of any other country, the fact that he has not surrendered the said passport on or before the 19 January 1963 shall be conclusive proof of his having voluntarily acquired the citizenship of that country before that date.
On 16 February 1962, a Constitution Bench of the Supreme Court of India held in the case of Izhar Ahmad Khan Vs. Union of India that "If it is shown that the person has acquired foreign citizenship either by naturalisation or registration, there can be no doubt that he ceases to be a citizen of India in consequence of such naturalisation or registration."
There now exists a provision for a new form of Indian nationality, the holders of which are to be known as Overseas Citizens of India. The Constitution of India does not permit dual citizenship or dual nationality, except for minors where the second nationality was involuntarily acquired. Indian authorities have interpreted the law to mean a person can't have a second country's passport simultaneously with an Indian one — even in the case of a child who is claimed by another country as a citizen of that country, and who may be required by the laws of the other country to use one of its passports for foreign travel (e.g., a child born in the United States to Indian parents) — and the Indian courts have given the executive branch wide discretion over this matter. Therefore, Overseas Citizenship of India is not a full citizenship of India and thus, does not amount to dual citizenship or dual nationality.
The Central Government may, on application, register any person as an Overseas Citizen of India if that Person is of Indian Origin and is from a country which allows dual citizenship in some form or the other. Broadly speaking, a "Person of Indian Origin" is a citizen of another country who:
Note that children of Indian parents do not automatically fulfill these requirements, and are therefore not automatically eligible for OCI.
Indian Missions are authorized to grant applications for Overseas citizenship of India within 15 days to cases where there is no involvement in serious offences like drug trafficking, moral turpitude, terrorist activities or anything leading to imprisonment of more than a year.
The introduction of Overseas Indian Citizenship does not entitle people who have acquired, or are planning to acquire, foreign nationality, to retain their Indian passports. The law continues to require that Indian citizens who take foreign nationality must immediately surrender their Indian passports. Those who are eligible can then apply for registration as Overseas Indian Citizens.
There is no plan to issue Indian passports to Overseas Citizens of India, although the registration certificate will be in the form of a passport-like booklet (similar to the #Person of Indian Origin (PIO) Card mentioned below). The Cabinet has also directed the Ministry of Overseas Indian Affairs to work on a proposal to give biometric smart cards to registered Overseas Citizens of India.
An Overseas Citizen of India will enjoy all rights and privileges available to Non-Resident Indians excluding the right to invest in agriculture and plantation properties. There is no visa requirement for travel to India. The person has to carry his existing foreign passport along with Registration Certificate. Alternatively, the Overseas Citizen of India can apply for a new type of visa called ‘U’ visa which is a multi-purpose, multiple-entry, life-long visa for those that wish to acquire it. It will entitle the Overseas Citizen of India to visit the country at any time for any length of time and for any purpose.
An Overseas Citizen of India will not enjoy the following rights even if resident in India: (i) the right to vote, (ii) the right to hold the offices of President, Vice-President, Judge of Supreme Court and High Court, Member of Lok sabha, Rajya Sabha, Legislative Assembly or Council, (iii) appointment to Public Services (Government Service). Also Overseas Citizens of India are not eligible for an inner line permit, they have to apply for a Protected area permit if they want to visit certain areas in India.
An interesting question is whether a person registered as an Overseas Citizen of India will lose the right of diplomatic protection by their home country while in India. Article 4 of the Hague Convention on Certain Questions relating to the Conflict of Nationality Laws of 1930 provides that "a State may not afford diplomatic protection to one of its nationals against a state whose nationality such person also possesses". The case depends on two things: first, does the Indian government itself recognize Overseas Citizenship of India as a true citizenship and on that basis refuse the right of diplomatic protection by the other country; and second, does the person's home country recognize it and accept India's refusal. Both points are doubtful. India does not give Overseas Citizens an independent travel document but instead puts a visa in the other country's passport. If a person is eligible to have only another country's passport but not any form of Indian travel document, it is hard to avoid the conclusion that the person is a sole citizen of the other country for the purposes of diplomatic protection.
Acquiring Overseas citizenship of India prevents British nationals from registering as full British citizens under Section 4B of the British Nationality Act of 1981 (which requires that nationals have no other citizenship in order to register.) It does not prevent them from acquiring full British citizenship by a different method and it does not revoke their British citizenship if they have already registered under Section 4B.

The Government of India's Public Information Bureau issued a press release which explains the Scheme for Overseas citizenship of India on 29 June 2005.
Full details of the OCI scheme can be found on the Government of India, Ministry of Home Affairs Web Page: (external link) http://mha.nic.in/oci/oci-main.htm
A number of other articles have been written including:
A PIO Card is generally valid for a period of fifteen years from the date of issue.
PIO holders can acquire, hold, transfer or dispose of immovable properties in India (except agricultural/ plantation properties), open rupee bank accounts in India, lend in rupees to Indian residents, make investments in India etc. PIO holders’ children can obtain admission in educational institutions in India in the general category quota for Non-Resident Indians, including Medical, Engineering colleges, IITs & IIMs. PIO holders are eligible for various Housing schemes under Life Insurance Corporation of India (LIC) or Central/State Governments. Possession of a PIO card will not entitle the holder to: (a) be eligible for the exercise of any political rights, (b) visit restricted/protected areas without permission, and (c) undertake mountaineering, research and missionary work without permission.
On commencement of the Indian Constitution on 26 January 1950, under British Nationality law a person who became an Indian citizen also had the status of Commonwealth citizen (also known as a British subject with Commonwealth citizenship, a status which does not entitle the person to use a British passport) by virtue of their Indian citizenship and India's membership of the Commonwealth. However, a number of Indians did not acquire Indian citizenship on commencement of the Indian Constitution and retained British subject without citizenship status (which entitles a person to a British passport) unless they had acquired citizenship of another Commonwealth country. Any person who is solely a British subject (otherwise than by connection with the Republic of Ireland) will automatically lose British subject status on acquiring any other nationality or citizenship including Indian citizenship or Indian Overseas citizenship.
British subjects may register as British citizens under section 4B of the British Nationality Act 1981 without requiring any UK residence if they have no other citizenship or nationality and have not after 4 July 2002 renounced, voluntarily relinquished or lost through action or inaction any citizenship or nationality. This facility has been available since 30 April 2003. Those who have immigrated to the UK may have additional options for acquiring British citizenship, which are usually preferred because they give transmissible British citizenship with otherwise than by descent status.
From 1949 the meaning of the term British subject was substantially different from what had previously been the case and meant little more than a term to describe someone holding the citizenship of a Commonwealth country. Only a British subject without citizenship was entitled to a British passport. See British subject.