Illegal immigration is the migration of people into a country in violation of the immigration laws of that country or the continuous residence without the legal right to live in that country. Illegal immigration tends to be financially upward, from poorer to richer countries. Illegal residence in another country creates the risk of detention, deportation, and/or other sanctions.
Asylum seekers who are denied asylum may face impediment to expulsion if the home country refuses to receive the person or if new asylum evidence emerges after the decision. In some cases, these people are considered illegal aliens. In others, they may receive a temporary residence permit, for example regarding the principle of non-refoulement in the International Refugee Convention. The European Court of Human Rights, referring to the European Convention on Human Rights, has shown in a number of indicative judgments that there are enforcement barriers to expulsion to certain countries, for example, due to the risk of torture.
The terminology surrounding illegal immigration is often controversial. In particular, describing people who immigrated illegally as illegal immigrants has been a matter of debate. It is nevertheless commonly used in formal contexts, among others by the United States and by the Canadian governments. Title 8 of the US Code is the portion of United States law that contains legislation on citizenship, nationality, and immigration. Defining the legal term alien as "any person, not a citizen or national of the United States," The terminology used in Title 8 includes illegal alien (33 times), unauthorized alien (21 times), undocumented alien (18 times), illegal immigrant (6 times), undocumented person (2 times), and others. An analysis by PolitiFact, however, concluded that the term illegal alien "occurs scarcely, often undefined or part of an introductory title or limited to apply to certain individuals convicted of felonies.