Following the disintegration of the Commonwealth during the turbulent Sturlung Age, Iceland fell under the control of the Norwegian king. Magnus VI of Norway drew up a law code for Iceland entitled Járnsíða. This law code restructured the traditional Icelandic system of government, removing power from the goðar, and increasing the power of the Norwegian king. A copy of Járnsíða is available online, or from the English Faculty Library.
Jónsbók is a formal codification of the laws, written in 1281 by Jón Einarsson. It superseded the earlier Járnsíða code.