Alien (law)

In law, an alien is generally any person (including an organization) who is not a citizen or a national of a specific country, although definitions and terminology differ across legal systems.

The term "alien" is derived from the Latin alienus. The Latin later came to mean a stranger, a foreigner, or someone not related by blood. Similar terms to "alien" in this context include foreigner and lander.

Different countries around the world use varying terms for aliens. The following are several types of aliens:

An "alien" in English law denoted any person born outside of the monarch's dominions and who did not owe allegiance to the monarch. Aliens were not allowed to own land and were subject to different taxes to subjects. This idea was passed on in the Commonwealth to other common law jurisdictions.

In Australia, citizenship is defined in the Australian nationality law. Non-citizens in Australia are permanent residents, temporary residents, or illegal residents (technically called "unlawful non-citizens"). Most non-citizens (including those who lack citizenship documents) traveling to Australia must obtain a visa prior to travel. The only exceptions to the rule are holders of New Zealand passports and citizenship, who may apply for a visa on arrival according to the Trans-Tasman Travel Arrangement.

In 2020, in Love v Commonwealth, the High Court of Australia ruled that Aboriginal Australians (as defined in Mabo v Queensland (No 2)) cannot be considered aliens under the Constitution of Australia, regardless of whether they were born in Australia or hold Australian citizenship.

In Canada, the term "alien" is not used in federal statutes. Instead, the term "foreign national" serves as its equivalent and is found in legal documents. The Immigration and Refugee Protection Act defines "foreign national" as "a person who is not a Canadian citizen or a permanent resident, and includes a stateless person."

In the United Kingdom, the British Nationality Act 1981 defines an alien as a person who is not a British citizen, a citizen of Ireland, a Commonwealth citizen, or a British protected person. The Aliens Act 1905, the British Nationality and Status of Aliens Act 1914 and the Aliens Restriction (Amendment) Act 1919 were all products of the turbulence in the early part of the 20th century.