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Nationality law (or citizenship law) is the
Nationality law can be broadly categorised into three principles,
Jus soli is the principle, whereby birth on a country's territorial jurisdiction; eg, 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, and this law was inherited by the colonies and subsequently codified into their own domestic laws, see United States, Canada, Australia, etc.
Jus soli laws aren't 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 citizenship if the child's father (regardless of nationality) was born in the same territory. Sometimes jus soli will be restricted by age.
There is also an intersection between the principles, where only persons of a certain race or blood, will acquire nationality at birth. For instance in Liberia, African born persons will acquire nationality, whereas those of non-African origin will not be entitled to this privilege.
Jus sanguinis is the principle whereby someone's blood dictates nationality of that person. For instance, in Italy; citizenship may be transmitted perpetually if one can find an Italian ancestor up until the founding of the Italian state in their lineage. Whereas 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. Cape Verde is a prominent example where upon marriage, and request for the citizenship, nationality is automatically conferred. Countries have in the past regarded marriage as an important status changing event in people's' lives and encouraged the special relationship that exists between spouses, sentiments which continue to be valued today. 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. Even after the nationality of a married woman was no longer dependent on the nationality of her husband, legal provisions were still retained which automatically
Nevertheless, state's rights to determine who their nationals are is not absolute and, in particular, States must comply with their human rights obligations concerning the granting and loss of nationality. In particular, citizens must not be arbitrarily deprived of their nationality. The right to a nationality and the prohibition against depriving ones nationality is codified in article 15 of
Article 1 of the
Most states today allow for aliens to acquire a nationality via a process known as