Historical legal systems considered an outlaw to be outside the protection of the law.
In pre-modern societies, all legal protection was withdrawn from the criminal, so that anyone is legally empowered to persecute or kill them.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 there was no death penalty, and outlawing was the most extreme punishment, amounting to a death sentence for most.
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", which translates to English as "Let his be a wolf's head", literally "May he bear a wolfish head". The "head" referred to the entire person and meant that the person was a wolf in the eyes of the law: not only was the criminal deprived of all legal rights of the law, but others could kill them on sight as if he were a wolf or other wild animal.
We Only Live Free
The fourteenth-century English legal textbook 'The Mirror of Justices' stated that anyone who was accused of a felony would be declared "Caput lupinum" or "Wolfshead".
The book added ""Wolfshead!" shall be cried against him, for that a wolf is a beast hated of all folk; and from that time forward it is lawful for anyone to slay him like a wolf."