An alien is a person who is not a citizen of the country in which they live. A resident alien is a person who has been allowed to permanently reside in the country by immigration authorities but has not been granted citizenship. Illegal aliens are those who have sneaked into the country or stayed beyond the time allowed on a visa. Aliens have certain due process rights under the Fourteenth Amendment of the U.S. Constitution. Alienage is a "suspect" classification in the context of equal protection legal analysis. The courts have held that alienage cannot be the basis for denying certain opportunities, such as education and civil service employment. However, aliens may be denied employment in position closely tied to the governmental functions of the state, such as teachers and police officers.