In historical legal systems, an outlaw is declared as outside the protection of the law. In pre-modern societies, the criminal is withdrawn all legal protection, so that anyone is legally empowered to persecute or kill them. Outlawry was thus one of the harshest penalties in the legal system. In early Germanic law, the death penalty is conspicuously absent, and outlawing is the most extreme punishment, presumably amounting to a death sentence in practice. The concept is known from Roman law, as the status of homo sacer, and persisted throughout the Middle Ages.
In the common law of England, a "Writ of Outlawry" made the pronouncement Caput lupinum ("Let his be a wolf's head", literally "May he bear a wolfish head") with respect to its subject, using "head" to refer to the entire person (cf. "per capita") and equating that person with a wolf in the eyes of the law: Not only was the subject deprived of all legal rights of the law being outside the "law", but others could kill him on sight as if he were a wolf or other wild animal. Women were declared "waived" rather than outlawed but it was effectively the same punishment.
Among other forms of exile, Roman law included the penalty of interdicere aquae et ignis ("to forbid water and fire"). People so penalized were required to leave Roman territory and forfeit their property. If they returned, they were effectively outlaws; providing them the use of fire or water was illegal, and they could be killed at will without legal penalty.
Interdicere aquae et ignis was traditionally imposed by the tribune of the plebs, and is attested to have been in use during the First Punic War of the third century BC by Cato the Elder. It was later also applied by many other officials, such as the Senate, magistrates, and Julius Caesar as a general and provincial governor during the Gallic Wars. It fell out of use during the early Empire.