wolf’s head.Hist. An outlaw, who was often referred to as carrying a wolf’s head (caput lupinum) and to be no more than a wild beast or wolf who could be slain and whose head could be carried to the king. — Also termed woolferthfod. See OUTLAW.

“Outlawry is the last weapon of ancient law, but one that it must often use. As has been well said, it is the sentence of death pronounced by a community which has no police constables or professional hangmen. To pursue the outlaw and knock him on the head as though he were a wild beast is the right and duty of every law-abiding man. ‘Let him bear the wolf’s head’: this phrase is in use even in the thirteenth century.” 1 Frederick Pollock & Frederic W. Maitland, The History of English Law Before the Time of Edward I 476 (2d ed. 1898).
[Blacks Law 8th]