Families & Friends Of Addicts Support Group

Its your house your rules. He will be mad, most likely try to put the blame on you like saying what were you doing in MY room, throw a fit trying to manipulate the situation. But he's a adult and adults need to have their own place. Set a date about one month from when he has to get his own place. YOu can't make him stop smoking pot but he doesn't have to do it in your house.
Its all about setting healthy boundaries.

Go About it?..... It's called boundaries. There should ALWAYS have been the boundary no drugs. The consequences, He is out.
All you need to do is show him the marijuana and say... "You know the consequences, you have 48 hours to get out,."
I know it sounds harsh... but this is about YOUR healthy boundaries and consequences and setting an example for him of what is right and wrong.
Good Luck.

Obviously this started before this incident per your frustrations. Boundaries boundaries boundaries. And they can start at anytime. Children are like Bonsai trees, we have to water them, trim them to grow into the shape that best fits. It takes love and discipline, and most people when asked think the opposite of love is hate, when it is actually lazy. It takes a lot of work to be consistent with our children, giving them lots of love but also getting them to know the consequences, and sticking to them. By the time they get to where yours is, it is hard but not impossible. It starts where it starts. Set your boundaries and do not sway from them. He is going to call you a hypocrite and fight it as he has been getting away with it, but to keep letting him rule the roost you are going to face a lot more pain in the long run. Nothing you can do about yesterday but you can start setting example today. I would not kick him out until you set these, then do what you need to do.