While on a family trip to Iceland, I read a translation of Njal's Saga. Granted, you have to read it in light of the fact that it wasn't written down until a long time after the events happened.

But it describes Iceland's ancient legal system in some detail. If you killed someone, you could be sued, tried, and fined. The fine went to the victim's family. What it looks like happened in practice was that the victim's family wasn't really satisfied that justice was done, and would conduct a revenge killing. Then the money would pass back to the other family again. The practical effect was that the entire saga is like a decades long blood feud, mediated by the court system.

Of course it was fascinating to read, especially since we were visiting places described in the saga, such as Thingvellier, where they met to conduct government and trials.

They had another system, where if you were utterly uncontrollable, they could vote you off the island by making you an outlaw, meaning that anybody could kill you without repercussion.