expulsion by executive agency of an alien whose presence in a country is deemed unlawful or detrimental. Deportation has often had a broader meaning, including exile, banishment, and the transportation of criminals to penal settlements.

In Roman law, deportation originally described a form of banishment for life to a foreign country, usually an island. Deportation was at first inflicted upon political criminals, but, in time, it became a means of removing those whose wealth and popularity rendered them objects of suspicion. It was also a punishment for adultery, murder, poisoning, forgery, embezzlement, and other crimes. Deportation was attended by the confiscation of property, loss of citizenship, and loss of civil rights. The practice of transporting criminals to foreign soil began in Europe in the 15th century, when Portugal sent convicts to South America, where they became some of the earliest settlers of Brazil. France initiated deportation during the Revolutionary period; the practice survived until 1938 despite much public criticism of the prison conditions on the islands of French Guiana, particularly the notorious Devil's Island. Peter I the Great of Russia ordered political prisoners to Siberia in 1710, thus beginning a practice that has continued through the 20th century.

In England deportation developed from the policy of allowing an arrested man the option to abjure the realm. He would take an oath to depart and never return. Often this represented the convict's only alternative to execution. Gradually a formal system of transportation of convicted criminals developed as a substitute for capital punishment. The inhuman treatment of criminals sentenced to servitude in the colonies of North America and Australia generated public pressure for penal reform, and the practice was abandoned in the 1850s.

In Anglo-American law today, deportation is a civil enactment imposed on persons who are neither native-born nor naturalized citizens. The alien is ordinarily, but not necessarily, returned to the country from which he came, usually because he has entered the deporting country illegally or without proper passport or visa. Aliens who become public charges, commit crimes involving moral turpitude, or engage in subversive activities can also be subjected to deportation proceedings. U.S. courts have shown leniency in circumstances in which families are split apart unjustifiably and left with no means of support.

Deportation differs from exclusion, extradition, and exile. Exclusion is the refusal by a governing authority to admit an alien. Extradition is the removal of a criminal to the country from which he has fled to avoid criminal prosecution or prison. Exile is a prolonged absence from one's country, either voluntary or by direction of the sovereign. See also exile and banishment; penal colony.