As I understand it, public notice of magic use of any kind gets Mordecai involved. The first thing they tell you is to stop it. The second thing is that there is a dampener device that they give registered magic citizens to mark them and to keep much of their power in check. And naturally, they watch you like a hawk because you're basically a dangerous second-class citizen, and infractions of the law further could be VERY painful or dead-making. So yeah, it's better that he left.
With that in mind, he could be bloody anywhere, couldn't he? I suppose part of what I might want to do is shaped by where he's going. And again, what kind of RP are you looking for with him?