Illegal immigration refers to immigration across national borders in a way that violates the immigration laws of the destination country. In politics, the term may imply a larger set of social issues and time constraints with disputed consequences in areas such as economy, social welfare, education, health care, slavery, prostitution, legal protections, voting rights, public services, and human rights. Conversely, Illegal emigration refers to unlawfully leaving a country.

Terminology

• illegal alien
• Illegal immigrant
• undocumented immigrant
• clandestine workers
• sans papiers/"without papers"

• Irregular immigrant/immigration
• undocumented immigrant/migrant/alien/worker/resident
• unauthorized immigrant/migrant/alien/worker/resident
• paperless immigrant/migrant/alien/worker/resident
• immigrant "without immigration status"
• out of status
• unnaturalized immigrant
• boat people

War

Illegal immigration may be prompted by the desire to escape civil war or repression in the country of origin. Non-economic push factors include persecution (religious and otherwise), frequent abuse, bullying, oppression, and genocide, and risks to civilians during war. Political motives traditionally motivate refugee flows - to escape dictatorship for instance.

After decades of armed conflict, roughly one of every 10 Colombians now lives abroad. For example, Colombians emigrating to Spain have "grown exponentially, from a little over 7,000 in 1993 to more than 80,000 in 2002 and 244,000 in 2003." Pilar Marrero, Immigration Shift: Many Latin Americans Choosing Spain Over U.S. Pacific News Service, December 9, 2004. Retrieved on 2008-09-02. This is equivalent to 124,000 Colombian immigrants in year 2003 into Spain alone. Also, figures from the U.S. Department of Homeland Security indicate that Colombia is the fourth-leading source country of unauthorized immigration to the United States. According to its estimates, the number of unauthorized Colombian residents in the United States almost tripled from 51,000 in 1990 to 141,000 in 2000.

El Salvador is another country which experienced substantial emigration as a result of civil war and repression. The largest per-capita source of immigrants to the United States comes from El Salvador. Up to a third of the world's Salvadoran-born population lives outside the country, mostly in the United States. Tania Snyder,To slow immigration from El Salvador, understand its causes Baltimore Sun, January 11, 2007 According to the Santa Clara County, California, Office of Human Relations.