Sounds like a fun character! Can't wait to see what happens with him at Tribunal...
Option one:
Freindly Frederico Flambonis (oh, and by the way, senior hoplite for the tribunal) pulls him aside and says, "You know, ______, I've got to say I've admired some of your handiwork. Others have noticed it as well. I have some ideas you might want to consider."
The magus replies, "But I haven't caused harm to my sodales!"
"Yes, indeed," Frederico continues, "this is why we are having this conversation. You'll have to be more circumspect, though, because you're making other folks nervous. If THESE folks get nervous, they may call for your March anyway and then I and my Friends will have to hunt you down." Frederico puts on a somewhat resigned face and says, "We won't enjoy it, mind you, but we will do it."
Brightening somewhat, F goes on, "Now, about those ideas..."
Option 2:
Grouchy Garranchus Guernicus (oh, by the way, number two Queasitor for the Tribunal) walks up to the magus, gets right in his grill, and points directly to his chest and says, "I have precisely one magus higher on my list than you, dogmeat, and I am tempted to divert my attention from him. Get a grip before your residency on that list is permanent."
Force him to get creative. There are rough guidlines for damage from rocks (ReTe and MuTe guidelines and spell examples in ArM5 and HoH:S), but I think one has to go to Art and Academe to correlate wounds to damage -- and from there you can construct your own guidelines.
-K!