Nationality law

Nationality law is the body of rules, set by a sovereign state and its internal jurisdictions, that determines how a person legally gains or loses national identity. Under international law, the process of acquiring nationality—formal membership in a nation—is distinct from the relationship between a national and the state, which is called citizenship. Some countries treat the two terms as interchangeable in their domestic laws, but by the 20th century, nationality had generally come to mean simply belonging to a particular nation, regardless of the type of government that defines the bond between the state and its people. In legal terms, nationality refers to a person's relationship with a state under international law, while citizenship refers to that person's relationship with the state under its own domestic statutes. Different regulatory bodies oversee compliance for each. A person who is not a national of a country is usually considered a foreigner or alien by that country. When territory is transferred from one state to another, individuals living there may be given the right to choose their nationality. A person with no recognized nationality in any jurisdiction is considered stateless. **Principles**

Nationality laws can be based on several principles. Three commonly discussed ones are:

- **Jus soli**, or the right of birth on the soil; - **Jus sanguinis**, or the right of the blood (descent); - **Jus matrimonii**, or the right of marriage. Laws often combine more than one route to nationality. Comparative data shows that unconditional jus soli is mostly found in the Americas, while many other states only offer conditional forms of birthright citizenship. **Jus soli**

Jus soli is the principle that being born within a country's territory can grant that country's nationality. In English common law, being born within the King's dominions generally meant owing allegiance to the Crown; this idea influenced nationality rules in British colonies and later the American concept of birthright citizenship. Jus soli is often conditional rather than absolute. For instance, Cambodia grants Khmer nationality at birth to a child born in Cambodia to foreign parents, but only if both parents were themselves born and legally living in Cambodia. Comparative citizenship data also distinguishes between unconditional and conditional territorial birthright regimes. Nationality rules can also include ancestry or racial qualifications. For example, Article 27(b) of Liberia's Constitution states that only people who are "Negroes or of Negro descent" can qualify by birth or naturalization to be citizens. **Jus sanguinis**

Jus sanguinis is the principle of acquiring nationality through descent, most often from a parent. Italy historically allowed transmission across multiple generations, but a law passed in 2025 restricted automatic citizenship for people born abroad who hold another citizenship. The current rules include exceptions where a parent or grandparent held only Italian citizenship, or where a parent or adoptive parent lived legally in Italy for at least two continuous years after gaining Italian citizenship and before the child's birth or adoption. **Jus matrimonii**

Some states allow nationality to be acquired through marriage. In Cape Verde, a foreigner married to a Cape Verdean national can acquire nationality by making a specific declaration during the marriage. At the start of the 20th century, many legal systems treated a married woman's nationality as tied to her husband's, so marrying a foreign man could automatically give her his nationality and cause her to lose her own. International reform efforts during the interwar period increasingly challenged this system. Some modern nationality laws explicitly state that marriage does not automatically change either spouse's nationality. Bulgaria's Citizenship Act, for example, says that entering or ending a marriage between a Bulgarian and a foreigner, or a change in one spouse's nationality during the marriage, does not automatically change the other spouse's nationality. Other states make naturalization easier for spouses; under Spain's Civil Code, a person married to a Spanish citizen may qualify after one year of legal residence, subject to statutory conditions. **Jus officii**

Uniquely, Vatican City citizenship is based on *jus officii*—that is, on being appointed to work in a certain capacity in service of the Holy See. It usually ends when the appointment ends. Citizenship may also be extended to the spouse and children of a citizen, provided they are authorized to live and are living together in the city. Anyone who loses Vatican citizenship and does not have another citizenship automatically becomes an Italian citizen, as provided in the Lateran Treaty. **Naturalization**

Naturalization is a common way for a non-national to acquire nationality, usually subject to residence and other statutory conditions. In GLOBALCIT's comparison of laws in force in 2020, five years was the most common 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 decide who it will recognize as its nationals and citizens. Such decisions may be based on custom, statutory law, case law (precedent), or a combination of these. In some cases, the decision may be governed by public international law—for example, by treaties and the European Convention on Nationality. However, states' rights to determine who their nationals are is not absolute; they must comply with their human rights obligations regarding the granting and loss of nationality. In particular, nationals must not be arbitrarily deprived of their nationality.