A Skogarmaor (meaning "man of the forest"), also called útlagi (meaning "outlaw"), is a Norse outcast who has been banished from their community for various crimes. Full outlawry was also called skóggangr (meaning "going into the forest"). Full outlawry meant that the outlaw lost his right to live as a full member of society for the rest of his life.
Viking political institutions had no formal law enforcement groups. It was left to the general populace to enforce laws. Since the laws were more or less just a codification of the social norms that people were expected to live by anyway, political leaders and legal assemblies typically had little problem getting the people to enforce the law themselves.
Instead of arresting and executing a person found guilty of severe crimes, the Norse declared them an outlaw. This meant that he no longer had any rights, all of his property was confiscated, and he could be lawfully killed by anyone. In a culture where honor-based revenge killing were commonplace and considered to be proper, this was often effectively a privatized death sentence.
The only way an outlaw could have their status as a skóggangr revoked was to pay a large sum of money to the political officials. By the end of the Viking Age these fines were important sources of revenue. There was also a "lesser outlawry," which meant that this period of banishment was limited to three years.
When Ivar was driven out of Kattegat, his bodyguards, including White Hair, were branded and disgraced by Bjorn. Declared outlaws, they went into banditry where they pilllaged, raped, and murdered folks throughout Norway. When they came upon Lagertha's village, they were met with resistance. In the first wave they lost a lot of men, however they managed to kill some of the folks and children, including Hali. In the second wave, the village had a series of booby traps, resulting in the death of most of the Skogarmaors. When the remaining bandits disengaged, White Hair stayed behind to continue to fight and was ultimately killed in a duel by Lagertha.
When King Harald ordered Bjorn to be killed, he sent one of the Skogarmaors among the assassins. As the outlaw prepares to attack Bjorn, he is ironicly killed by another outlaw: Erik the Red. Erik was made a commander of Kattegat's forces in return for rescuing Bjorn.
When Bjorn discovered that a drunk Hvitserk had killed Lagertha after thinking that Ivar was coming to kill him, he decided to exile him after realizing he would be happy to die. Hvitserk was forbidden from entering any civilized place. He was, however, rescued by Ivar who was accompanying a Rus scouting party to Kattegat and taken to Kiev, where he agreed to assist the Rus in conquering Scandinavia.