That philosophy predates Icelandic and Ireland, England and Scotland and comes from old Norse law...
"In the instance of outlawry, or irredeemable crimes, Viking law "did not aspire to improve the moral condition of the criminal and try to make him a better man, except through the fear of punishment." Rather, the object of Viking law with respect to irredeemable crimes was "to prevent private revenge, and stop people taking matters into their own hands." Irredeemable crimes were punished by the confiscation of all property from an offender and the outlawing of the offender from society. Murder was one of the irredeemable crimes. "Men could be slain with impunity, and were irredeemable" by a free man "if they were found guilty with the following women" . . . one's wife, sister, daughter, mother, stepmother, brother's wife, or son's wife. The slaying of a lawman was also considered to be an irredeemable crime. Under Viking law, "an insane man who committed murder, though no accounted responsible for his actions, was expelled from the country."
Gotta love the thought process of my Ancestors.....