At Rome, in early times, exile was not a punishment, but rather a means of escaping punishment. Before judgment had been finally pronounced it was open to any Roman citizen condemned to death to escape the penalty by voluntary exile (_solum vertere exsilii causa_). To prevent his return, he was interdicted from the use of fire and water; if he broke the interdict and returned, any one had the right to put him to death. The _aquae et ignis_ (to which _et tecti_ "shelter" is sometimes added) _interdictio_ is variously explained as exclusion from the necessaries of life, from the symbols of civic communion, or from "the marks of a pure society, which the criminal would defile by his further use of them." Subsequently (probably at the time of the Gracchi) it became a recognized legal penalty, practically equivalent to "exile," taking the place of capital punishment. The criminal was permitted to withdraw from the city _after_ sentence was pronounced; but in order that this withdrawal might as far as possible bear the character of a punishment, his departure was sanctioned by a decree of the people which declared his exile permanent. Authorities are not agreed whether this exile by interdiction entailed loss of _civitas_; according to some this did not ensue until (as in earlier times) the criminal had assumed the citizenship of the state in which he had taken refuge and thereby lost his rights as a citizen of Rome, while others hold that it was not until the time of Tiberius (A.D. 23) that _capitis deminutio media_ became the direct consequence of trial and conviction. _Interdictio_ was the punishment for treason, murder, arson and other serious offences which came under the cognizance of the _quaestiones perpetuae_ (permanent judicial commissions for certain offences); confiscation of property was only inflicted in extreme cases.
Under the Empire _interdictio_ gradually fell into disuse and a new form of banishment, introduced by Augustus, called _deportatio_, generally _in insulam_, took its place. For some time the two probably existed side by side. _Deportatio_ consisted in transportation for life to an island (or some place prescribed on the mainland, not of Italy), accompanied by loss of _civitas_ and all civil rights, and confiscation of property. The most dreaded places of exile were the islands of Gyarus, Sardinia, an oasis in the desert (_quasi in insulam_) of Libya; Crete, Cyprus and Rhodes were considered more tolerable. Large bodies of persons were also transported in this manner; thus Tiberius sent 4000 freedmen to Sardinia for Jewish or Egyptian superstitious practices. _Deportatio_ was originally inflicted upon political criminals, but in course of time became more particularly a means of removing those whose wealth and popularity rendered them objects of suspicion. It was also a punishment for the following offences: adultery, murder, poisoning, forgery, embezzlement, sacrilege and certain cases of immorality.