|Legal status of persons|
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.: 66–67 : 338 : 73 Some nations domestically use the terms interchangeably,: 61, Part II : 1–2 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.: 1707–1708 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.: 4 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. A person who has no recognised nationality to any jurisdiction is regarded as stateless.
Nationality law can be broadly categorized into three principles:
Laws may be based on any one of these principles, but they commonly reflect a combination of all three principles. Generally speaking, countries in the Americas have a strong jus soli heritage.
Main article: Jus soli
Jus soli is the principle, whereby birth on a country's territorial jurisdiction—e.g., land, or in some cases, vessel registered as being registered as under the jurisdiction of that country (aeroplanes, ships)—confers nationality of the country of birth to the child. In most countries, this originated from the English common law tradition that all persons born on the King's land owed an allegiance to the King. This law was inherited by the colonies and subsequently codified into their own domestic laws, such as in the United States, Canada, Australia, etc.
Jus soli laws are not always absolute: sometimes countries with jus soli laws require lawful residence in the country before the authorities will observe this right, such as in Cambodia or Thailand. Sometimes jus soli laws only operate generationally, such as in some Middle-Eastern countries, where a child born in the territory will only acquire nationality if the child's father (regardless of parental nationality) was born in the same territory. Sometimes jus soli will be restricted by age.
There is also an intersection between the principles, wherein only persons of a certain race or blood will acquire nationality at birth. For instance, in Liberia, African-born persons will acquire nationality while those of non-African origin will not be entitled to this privilege.
Main article: Jus sanguinis
Jus sanguinis is the principle whereby the nationality of a person is dictated by their blood (i.e., parentage or ancestry). For instance, in Italy, nationality may be transmitted perpetually if one can find an Italian ancestor up until the founding of the Italian state in their lineage. By contrast, other states may restrict their jus sanguinis transmission of nationality up to the registration of the second generation down the family line.
Some states automatically confer nationality on the basis of marriage. A prominent example of a country with jus matrimonii laws is Cape Verde.
The common practice within and among states at the beginning of the 20th century was that a woman should have the nationality of her husband; i.e., upon marrying a foreigner, the wife would automatically acquire the nationality of her husband and lose her previous nationality, often with the reciprocal recognition by the other country. Legal provisions existed that automatically naturalised married women, and sometimes married men as well. This led to a number of problems, such as: loss of the spouses' original nationality; spouses losing the right to consular assistance, as such cannot be provided to nationals under the jurisdiction of a foreign state of which they are also nationals; and men becoming subject to military service obligations.
There has been a shift towards a principle that neither marriage nor dissolution of marriage automatically affecting the nationality of either spouse, nor of a change of nationality by one spouse during marriage automatically affecting the nationality of their spouse. However, in many jurisdictions spouses can still obtain special and fast processing of applications for naturalisation.
Main article: Naturalization
Most states today allow for aliens to acquire a nationality via a process known as naturalization on the basis of long-term residence and other conditions. This process and the conditions it entails are detailed in the states' nationality laws. Some nationality laws have special provisions to make it easier for diaspora populations to become nationals.
By international custom, each sovereign state generally has the right to freely determine who it will recognise as its nationals and citizens. 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. The right to a nationality and the prohibition against depriving one's nationality is 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:
The "Inter-American Court of Human Rights" went further in limiting state's right to determine nationality:
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