Rome canonised the Viking king Olav for forcibly converting his countrymen to Catholicism. He thought the new religion would strengthen his position, but his successors found themselves taking orders from a distant pope who bound them with a concordat.
King Magnus VI, known as "the Law-Mender", issued the first Western secular law code. However, just three years later he was forced by the concordat to hand over to the Church jurisdiction over anything that it considered to fall within its sphere. The list of these "Church matters" in article 2 of this summary shows how the concordat put people back under its laws and its courts.
As the concordat's introduction makes clear, this was a settlement between the Archbishop and the King made quietly, with no endorsement by parliament. The Vatican treaty overturned traditional law by giving the Church vast new powers over the people. Doubtless for the sake of the ailing king, the concordat is depicted as a way to help its signatories achieve "salvation for their souls".