An outlaw, in its original and legal meaning, is a person declared as outside the protection of the law. In pre-modern societies, all legal protection was withdrawn from the criminal, so anyone was legally empowered to persecute or kill them.
To declare illegal: outlawed the sale of firearms. 2. To place under a ban; prohibit: outlawed smoking in the house. 3. To deprive (one declared to be a criminal fugitive) of the protection of the law.