Immigration law is the branch of a country's legal system wherein legislation, custom and court precedent combine to define the ways in which that country's nationality and citizenship are transmitted, acquired or lost. Nationality law is often discussed or studied along with immigration law (for those immigrant-receiving countries such as the United States, Canada, Australia and New Zealand) and with refugee or asylum law.

Common principles

Immigration law in Continental and is based upon the Napoleonic Code which established that for purposes of nationality, that of the father was primary. For many years, therefore, in Europe and in former European colonies, women could not transmit their nationality to their children born in wedlock (those children born outside of marriage could often acquire their mother's nationality as there were provisions so that no child would be stateless). Many of these laws have since been changed, with the Arab states being an exception. In many Arab states, women married to foreigners cannot transmit their nationality to their children. [1] Many countries also have provisions stating that native-born children of accredited foreign diplomatic staff/officers do not acquire that nationality.

Article 15 of the Universal Declaration of Human Rights states:

1. Everyone has the right to a nationality.

2. No one shall be arbitrarily deprived of his nationality nor denied the right to change his nationality.

Today, nationality law is based either on jus soli or jus sanguinis, or on a combination of the two. Jus soli is the principle in which a child born in a country's territorial jurisdiction acquires that country's nationality (Ex: United States, Canada, Argentina, Brazil, Mexico, France [including in its overseas dependencies]). In jus sanguinis, either the father or mother must normally be a citizen of the country in question in order for the child to be a citizen (e.g. Israel, Switzerland).

Nationality issues in post-colonial context

Often in post-colonial situations, sorting out the nationalities of settlers, colonists and subjects was difficult and often a highly politically-charged process, particularly in the United Kingdom and in so-called settler colonies of Africa, such as South Africa, Rhodesia (now called Zimbabwe), Uganda and Hong Kong.

Immigration itself is the movement of people from one nation-state to another. While human migration has existed throughout human history, immigration implies long-term permanent residence (and often eventual citizenship) by the immigrants: tourists and short-term visitors are not considered immigrants (see expatriates). However, seasonal labour migration (typically for periods of less than a year) is often treated as a form of immigration. The global volume of immigration is high in absolute terms, but low in relative terms. The International Intergration and Refugee Assosiation estimated 190 million international migrants in 2005, about 3 percent of global population. The other 97 percent still live in the state in which they were born, or its successor state. The Middle East, some parts of Europe, little areas of South East Asia, and a few spots in the West Indies have the highest numbers of immigration population recorded by the UN Census 2005.

The modern idea of immigration is related to the development of nation-states and nationality law. Citizenship of a nation-state confers an inalienable right of residence in that state, but residence of immigrants is subject to conditions set by immigration law. The nation-state made immigration a political issue: by definition it is the homeland of a nation defined by shared ethnicity and/or culture, and in most cases immigrants have a different ethnicity and culture. This has led to social tensions, xenophobia, and conflicts about national identity, in many developed countries. Illegal immigration refers to immigration across national borders in a way that violates the immigration laws of the destination country. Under this definition, an illegal immigrant is a foreigner who either illegally crossed an international political border, be it by land, sea or air, or a foreigner who legally entered a country but nevertheless overstay their visa in order to live and/or work therein.