The Norwegian Law of Succession (Tronfølgeloven av 1163) was first introduced in 1163 during the Civil war era in Norway.
The Succession law was an accord between Erling Skakke and Øystein Erlendsson, Archbishop of Nidaros.
They had a son, Magnus Erlingsson, who was deemed to be a legitimate claimant to the throne, which was left vacant with the death of King Haakon II.
Archbishop Erlendsson agreed to terms under which Magnus inherited the Norwegian throne, in exchange for greater power afforded to the Church.
If the king had no suitable heir, the council could choose whoever they thought would better "guard God's right and the laws of the land".