Originally Posted by
Lokasenna
One of the main genres of saga literature, the Icelandic Family Sagas (Íslendingasögur) are overwhelmingly concerned with feuds between various Icelandic families - indeed, one can even think of it as a feud-based culture. There's nothing like a long-held and bloody-minded grudge to keep you warm through the long, cold winter nights.
One of the fascinating things about the Icelandic Commonwealth (930-1262) is that it had a very elaborate legal system, but no government or enforcing authority: no kings, no soldiers, no police. This meant that if someone wronged you, you could prosecute them at court; if the court found in your favour, however, it was your responsibility to enact their decision. So if for example someone gave you a mortal insult and this was proven, the court would decree that you could kill that person without yourself being able to be prosecuted for murder.
Of course, in many sagas the characters end up acting outside the bounds of the court, taking unlegislated vengeance against each other: by the end of many of the sagas, there is usually a fairly high body count, not to mention the fact that the original cause of the feud has probably long since been forgotten.