I don't allow smoking of any kind in our house. It's a non smoking house.. So he would have to leave if it were me. All the more would he go if he wouldn't work, pay rent, treat us respectfully etc
It isn't about what is legal or not to me. He is a guest in your house. At 21 if he can't be a nice guest, and won't be productive or follow our house rules, which are not the same as legal laws, I would give him three months to leave.
If pot were legal in my state and my kid smoked it and had a job, paid the rent, was respectful, etc. he could stay if he always smoked either pot or cigarettes off of my property. Not in my yard. Off the property. I hate the smell of pot and the effects of nicotine in my lungs. I dont want cigarette butts on my property either. Hub and I choose to be smoke free. Even our friends and other family can't pollute our lungs with smoke in our house. Nobody can. And disrespect at 21? Bye.
Your house/your rules. When he is in his own place and is 100 percent on his own he can make his own house rules in his own place. That means ...as in on his own and not taking a dime from you. Until that day, you can make any rules and stop helping out if he won't comply. A person is on his own when he is fully self supporting. Not getting "help" from the folks.
He is not a little boy. At 18 he can serve our country. Many do.
He is a man. He is able bodied. He can find a job and roommates and move out. Or there are shelters. Or he can follow your house rules. You would not be throwing him out. If he doesn't like the rules he would be choosing to leave. Some prefer homelessness to respect and a job and following any rules. That is their choice. I made my daughter leave for drugs and she got it together fast and quit. She has a good life now.
You and wife need to be on the same page. If not, I recommend marital therapy.