Is it just for a little bit that he's smoking, or is like constant chain smoking? To where, you could close up your window until he's done with his smoke and then open back up?
I'm glad I don't have this issue, just had a problem one time, but held my tongue. SIL came to visit/help when my LO was born. Since it was middle of summer, and it was just starting to cool off for the evening, I had my bedroom window open, while I rocked LO to sleep. She walks right past, smiles at me and proceeds to smoke POT.