@ossobuco,
To be serious, I've no idea if he smokes it too much and not responsibly.
I can see why he might want to leave you all moral insistors.
A large amount of americans, which I am guessing you are, leave people some room to smoke marijuana.
I can see though, that if I hated it, I wouldn't want to be married to anyone who smoked it, so I get your mother's point of view, and it is her house too, and you are on her side.
He might smoke too much, plus in the house, and that is a concern.
They need to work their stuff out.