Unfortunately you are in a bad spot. There is no easy fix here. You must establish long term plans and goals to survive it as a caretaker.
It might be legal but you are in charge of any and all rules in your home. When my daughter brought pot into my home, I called the cops immediately and it scared the hell out of her and that ended. However, that was only a short term fix and did not really help long term as she started shooting heroin… Cant really blame her for it as it was a way to escape SZ… I sent her out of state for a 60 day dual purpose treatment and it worked. In my opinion, you must take a hard stand or it will get much worse with the drugs. Hard love, he must understand that even as an adult when he turns 18 he still lives under your rules or live on the streets. These rehabilitation insurance cash cows are very popular nation wide and they do work for some. We contacted Beaches below and my daughter was on a plane to Florida the same day!!!