As a supporter of the king, Arnbjørn is reported to have replied: "May be that our lawmen have said this when they had more in them of mead- less than of the laws of Saint Olaf.
[8] In 1225, he had 400 men under his command and was supposed to meet the king at a place called Eidawood but saw the Ribbalds and chased them to Oslo, but they escaped.
[9] The local bishop, who was his foster father and friend, persuaded Arnbjorn to stay to give him counsel despite his wishes to push on to the king.
The king sent one of Arnbjorn's followers, Olaf Swim-Strong, to tell the Ribbalds to hold their words and wait for the battle.
[15] In 1239, when the king was preparing to go to war with the newly elevated Duke Skule Bårdsson, he sent word to Arnbjørn to raise his levies.