The "big hammer" is that you have the EC license- not him- so YOU are the real expert, the final authority.
I did have, at one place, some folks who looked for mischeif to cause. I rigged a radio ro a motor starter and a light beam....wheneve someone broke the beam, the music stopped- giving fair warning. (The beam was placed where they couldn't hear the music, so they never realised whay was happening).
Most likely, the guy realises all too well his limitations, and will stay away. Heck, if you pretend to be nice, he may come to you for advice and help! He can be a real asset- someone needs to patch the walls after you're done!
