Nationality law is the law of a sovereign state, and of each of its jurisdictions, that defines the legal manner in which a national identity is acquired and how it may be lost. In international law, the legal means to acquire nationality and formal membership in a nation are separated from the relationship between a national and the nation, known as citizenship. Some nations domestically use the terms interchangeably, though by the 20th century, nationality had commonly come to mean the status of belonging to a particular nation with no regard to the type of governance which established a relationship between the nation and its people. In law, nationality describes the relationship of a national to the state under international law and citizenship describes the relationship of a citizen within the state under domestic statutes. Different regulatory agencies monitor legal compliance for nationality and citizenship. A person in a country of which he or she is not a national is generally regarded by that country as a foreigner or alien. When the sovereignty over a territory is transferred from one state to another, individuals may be given the right of option of nationality. A person who has no recognised nationality to any jurisdiction is regarded as stateless.
Principles Nationality laws can use several bases for acquisition. Three commonly discussed bases are:
jus soli, or right by birth on the soil; jus sanguinis, or right of the blood; and jus matrimonii, or right of marriage.
Laws may combine more than one route to nationality. Comparative data show that unconditional jus soli is concentrated in the Americas, while many other states provide only conditional forms of birthright citizenship.
Jus soli
Jus soli is the principle whereby birth within a country's territory can confer that country's nationality. In English common law, birth within the King's dominions generally entailed allegiance to the Crown; that doctrine influenced nationality rules in British colonies and the later American understanding of birthright citizenship.
Jus soli is often conditional rather than absolute. Cambodia, for example, grants Khmer nationality at birth to a child born in Cambodia to foreign parents when both parents were themselves born and legally resident in Cambodia. Comparative citizenship-law data likewise distinguish unconditional from conditional territorial birthright regimes.
Nationality rules may also contain ancestry or racial qualifications. Article 27(b) of the Constitution of Liberia states that only persons who are "Negroes or of Negro descent" qualify by birth or naturalization to be citizens of Liberia.
Jus sanguinis
Jus sanguinis is the principle of acquiring nationality through descent, most commonly from a parent. Italy historically permitted transmission across multiple generations, but legislation enacted in 2025 restricted automatic citizenship for people born abroad who hold another citizenship. The current rules include exceptions where a parent or grandparent held exclusively Italian citizenship, or where a parent or adoptive parent resided legally in Italy for at least two continuous years after acquiring Italian citizenship and before the child's birth or adoption.
Jus matrimonii Some states allow nationality to be acquired on the basis of marriage. In Cape Verde, a foreigner married to a Cape Verdean national may acquire nationality by making the prescribed declaration during the marriage.
At the beginning of the 20th century, many legal systems treated a married woman's nationality as dependent on her husband's, so marriage to a foreign man could automatically confer the husband's nationality and cause loss of the woman's prior nationality. International reform efforts during the interwar period increasingly challenged this system.
Some modern nationality statutes expressly provide that marriage does not automatically change either spouse's nationality. Bulgaria's Citizenship Act, for example, states that concluding or dissolving a marriage between a Bulgarian citizen and a foreign citizen, or a change in one spouse's nationality during marriage, does not automatically change the other spouse's nationality. Other states facilitate naturalization for spouses; under Spain's Civil Code, a person married to a Spanish citizen may qualify after one year of legal residence, subject to the statutory conditions.
Jus officii
Uniquely, citizenship of the Vatican City is jus officii, namely on the grounds of appointment to work in a certain capacity in the service of the Holy See. It usually ceases upon cessation of the appointment. Citizenship may also be extended to the spouse and children of a citizen, provided they are authorized to reside and are living together in the city. Anyone who loses Vatican citizenship and does not possess other citizenship automatically becomes an Italian citizen as provided in the Lateran Treaty.
Naturalization
Naturalization is a common route by which a non-national may acquire nationality, generally subject to residence and other statutory conditions. In GLOBALCIT's comparison of laws in force in 2020, five years was the most frequent nominal residence requirement, and most countries with a residence-based route required no more than ten years.
Limits to nationality law By international custom, each sovereign state generally has the right to freely determine who it will recognise as its nationals and citizens.de Groot, Gerard-René. 2006. "Nationality Law." Pp. 476–92 in Elgar Encyclopedia of Comparative Law, edited by J. Smiths. p. 479. Edward Elgar Publishing. Such determinations may be made by custom, statutory law, case law (precedent), or a combination of either. In some cases, the determination may be governed by public international law—e.g., by treaties and the European Convention on Nationality.
Nevertheless, states' rights to determine who their nationals are is not absolute, and states must comply with their human rights obligations concerning the granting and loss of nationality. In particular, nationals must not be arbitrarily deprived of their nationality."Right to a Nationality and Statelessness." OHCHR.org. Office of the United Nations High Commissioner for Human Rights. The right to a nationality and the prohibition against arbitrary deprivation of nationality are codified in article 15 of the "Universal Declaration of Human Rights".
Article 1 of the "Convention on Certain Questions Relating to the Conflict of Nationality Laws" states:"Convention on Certain Questions Relating to the Conflict of Nationality Laws." League of Nations. 1930. Archived from the original on 26 December 2014.
It is for each State to determine under its own law who are its nationals. This law shall be recognised by other States in so far as it is consistent with international conventions, international custom, and the principles of law generally recognised with regard to nationality.
The "Inter-American Court of Human Rights" went further in limiting state's right to determine nationality:"Proposed Amendments to the Naturalization Provisions of the Constitution of Costa Rica." Advisory Opinion OC 4/84. Inter-American Court of Human Rights. 19 January 1984. § 3, para. 32, p. 9.
[T]he manners in which States regulate matters bearing on nationality cannot today be deemed within their sole jurisdiction; [the powers enjoyed by the States in that area] are also circumscribed by their obligations to ensure the full protection of human rights.
Ethnic group-related provisions, by country Some nationality and immigration laws provide facilitated acquisition or residence for emigrants, descendants, or persons of specified national or ethnic origin. A non-exhaustive list follows.
Armenia
Article 14 of the Constitution of Armenia (1995) provides that "individuals of Armenian origin shall acquire nationality of the Republic of Armenia through a simplified procedure." This provision is consistent with the Declaration on Independence of Armenia, issued by the Supreme Soviet of Armenia in 1990, which declared, in article 4, that "Armenians living abroad are entitled to the citizenship of the Republic of Armenia."
Bulgaria
According to the Constitution of Bulgaria, Article 25(2): "A person of Bulgarian origin shall acquire Bulgarian nationality through a facilitated procedure."
Chapter Two of the Bulgarian Citizenship Act governs acquisition of Bulgarian citizenship. Article 9 recognizes citizenship by origin where descent from a Bulgarian citizen is established in the manner provided by law, while Article 15 provides facilitated naturalization for a person of Bulgarian origin.
China
Chinese law provides special protections and appropriate preferential treatment to returned Overseas Chinese, a term that refers to Chinese citizens who had settled abroad and returned to China for permanent residence. The "rights and interests of returned overseas Chinese" are afforded special protection according to Articles 50 and 89(12) of the Chinese Constitution.
Hong Kong
In April 2015, the Hong Kong Government announced a pilot scheme named "Admission Scheme for the Second Generation of Chinese Hong Kong Permanent Residents" (ASSG).Government of Hong Kong. 28 April 2015. "Immigration Department to implement pilot Admission Scheme for 2nd Generation of Chinese HK Permanent Residents & enhancements to talent admission arrangements" (press release).
Taiwan
Taiwan's immigration rules distinguish Republic of China nationals without household registration in the Taiwan Area from nationals who have household registration. The National Immigration Agency maintains specific procedures governing the stay of nationals without household registration.
Since 1 January 2024, nationals without household registration who hold a valid biometric Republic of China passport and confirmed return or onward tickets may enter without first applying for an entry permit, subject to statutory exclusions; holders of valid non-biometric Republic of China passports must apply for a temporary entry permit on arrival.
Czech Republic The Czech Republic grants nationality at birth to a child if at least one parent is a Czech national; Czech law permits dual or multiple nationality. Moreover, people of Czech origin might be granted the right to permanent residence (Czech origin is a reason worth of consideration).
In 1995, the Czech Republic amended its Nationality Law to provide the Interior Ministry with the discretion to waive the usual five-year residency requirement for foreigners that had been resettled in the Czech Republic by 31 December 1994. This amendment was aimed particularly at several hundred ethnic Czechs which had been brought by the Czech government from the Ukrainian region of Volhynia, and was of a limited duration. The amendment was consistent with what the Czech Ministry of Labor and Social Affairs has identified as "the Czech government's policy principles regarding the resettlement of foreigners of Czech origin living abroad." A private fund, the People In Need Czech Television Foundation, worked with government authorities between 1995 and 2001 to effect this resettlement in the specific instance of Russian and Kazakh nationals of Czech origin, and had resettled approximately 750 such persons as of 2000.
Finland
The Finnish Aliens Act provides residence-permit routes on remigration grounds for certain people with Finnish roots. The Finnish Immigration Service identifies eligible categories including former Finnish citizens and descendants who have at least one parent or grandparent who is or was a Finnish citizen by birth.