I wouldn't call it a precedent exactly. In Charlemagne's time there was still some holdover from the time when the Church protected "wonder-workers" (wizards, magicians etc) from the authorities and the only rule was "don't invoke demons". Even that was not as significant as it became later, when attitudes to the Devil changed in the course of the Middle Ages. Up until then the Devil was seen as a sort of buffoon and stories focus on mortals getting the better of him and indeed making a fool of him (in some areas this tradition continued; I was brought up on stories like that). This brought about a change in attitude to anybody suspected of dealing with him or his minions.