I def would not be happy about anyone doing anything that stunk out my house with an unwanted smell. Least not my sons room.
Try the 'softly, softly' approach. If that fails then seek whom ever agency would deal with this were you are. I would not be any more confrontational. Assertive yes, but no getting into big arguments etc etc. Give them no ammunition if they turn out to be idiots!
Here in the UK I'd call somebody from the local council. Not sure whether the police would involve themselves at this point?
TBH if the 'softly softly' approach doesn't work then they are ****s and deserving of wrath! Hopefully they just don't realize the smell is carrying and like any right minded person dose something about it of their own back.
Cus smoking and tripping is all that you do. Ohhhh yeaahhh