Thank you all for your responses. I think that CatsPajamas hit the nail on the head as I needed to hear it and already know it...the difference is we are married, both on the mortgage, etc.
I am not willing to live with anyone using/possessing drugs in my home. I set this boundary over 15 years ago with my children's father and left when he refused to adhere. In that situation, however, we were not married, and my name was not on the mortgage. Much easier and less complicated to walk away...other than becoming a single mom-which I was basically doing anyway, just not physically. I have allowed this boundary to be crossed, and I have been puzzled as to why. I realize it's because I am married to this man and feel that marriage is for life, etc, etc. However, I also know that active addiction is a deal breaker (Dr. Phil). In the past (a few months ago), I would take the kids and leave if I knew he was using in the house. I would spend the night at his sister's or my best friend's house. However, now my kids are back in school and that is a little more inconvenient for them, very disruptive. I feel that I'm in a rock and a hard place. I have asked him to leave on many occasions in the past when he crossed this boundary, and of course, he wouldn't...told me I knew where the door was.
So, with all that said, I know in my heart and have known all along, the only way to get him to leave is to file a restraining order. I refuse to leave my home, I will not do it on a permanent basis. I have no family in this state, and my kids deserve the stability of the same home over their head. Besides, he is the one screwing up. He needs to be the one to go if he can't respect this boundary.
OK, with that said...if I ever get to the point of knowing that I can and will enforce this boundary, how do I relay to him what the consequence is for crossing it? Do I sit down and have a conversation with him during a sober moment...hey, honey, if you cross this boundary, I'm going to expect you to leave, and if you don't, I'll file a motion that says you can't come back home?? I mean, wouldn't that really **** him off and cause a big fight...is there just no way around that?