Please do not use the term "kicking him out." That term makes him a victim of your aggressiveness.
What really happened here is that your son chose to not live in your home because he does not want to abide by the rules. He's just not keeping his end of the contract by voluntarily leaving. What he is doing is "squatting" which leaves you to move him along. It's a very typical MO for addicts.
I second Ann's advice. For your peace of mind, have a printed list of phone numbers, addresses, whatever, to hand to him as you have this conversation with him tonight. If he is anything like my son, he will not even pick it up. But it may help you feel a little better as you see him walk out the door with his addict designer luggage (black garbage bags).
((Hugs))