Love him enough to throw him out. Its all you can do. You are right that "I cannot help him if he is refusing treatment."
Find him a rehab or a sober living if you can, so that you can offer to drop him off, but if he won't go with you, then yes, let him make his own decision about where to live if he is over 18. Just not with you.

How old is your son? This is your house and you need to set some house rules. For example, if he lives there he helps out no excuses. He is not to do drugs in your house and since meetings aren't working I would suggest he go to counseling with an addictions coach or one who specializes in addictions. If he does not want to follow the house rules then he must find another place to stay. The number one problem parents have is giving in too many times. The addict knows this they so push us even further. Here is some do's and don't and also on monday nights Smart Recovery has Friends and Family meetings online which are very informative. http://www.smartrecovery.org/resources/library/For_Family_Volunteers_Professionals/those_who_care.htmhttp://www.smartrecovery.org/resources/family.htm

I have been where you are, as many of us have. Look your self in the mirror and tell yourself enough! It is the hardest thing you will have to do as a parent, as it was for me, but it also made the difference in my son getting treatment. I don't know what will happen, but I do know that enabling does not help, his choice, he wants to use he cannot live in your home it's that simple. ( I know it doesn't feel that simple)

I'm sorry. I've been in your shoes, with the exception of the overdose. It's an impossible situation. You set rules, but they aren't followed and now it's time for consequences. But, the law doesn't always make it easy to provide consequences for our kids and the addiction does things to an addict's brain that makes it hard for them to understand consequences.

When my son went to his dealer's house (where he was forbidden to go), I refused to go pick him up. He walked to a police station and got a ride home and I got a lecture from the officer that I'm required to let him come home as long as he's under 18. Yet a teenager does have the right to refuse treatment, which puts parents in an impossible situation.

I see from your profile that your son is addicted to pain meds. If these are opiates, then I highly recommend getting him into a program that provides Suboxone, Vivitrol or methadone. Some people will disagree with this recommendation, but it has been a lifesaver for many. I have a friend whose son has been on methadone for two years. He's being weaned off and will be completely clean next week and committed to sobriety. My son has been on methadone for almost a year and says it saved his life. I have another friend whose daughter had a horrible addiction to heroin and failed repeatedly at getting sober. She's been on methadone for 4 months now and is living a normal life, getting along with her family, and working a job.

I am reading a book called Healing the Addicted Brain right now that explains the science behind why addicts act the way they do and what it does to their brains. It explains why he lies and why he would refuse treatment even after an overdose. It also gives good recommendations on how to heal the brain to get back to normal behavior.

I also recommend the book Don't Let Your Kids Kill You. It will help you to let him go if he refuses to help himself.

I want to thank you all for your helpful advice, believe me it really is helpful and comforting to hear from people that have already been through this. My husband and I told my son that everything stops immediately. He is giving a half attempt of going to meetings and counseling and still using. He knows he is no longer fooling us. He is angry because he knows the next slip up, he is out the door! Still denying rehab. I told him I can no longer allow him to slowly kill himself in my home, he has to want the help and must do it for him, not for me! Let's see where this goes, but I know I have to be strong and stick to my word. Enough of these empty threats because they are getting us no where.

Your last sentence is the most important thing you will ever say...Please, stick to your word. say it, mean it, do it. otherwise, addiction wins.
It is so hard. I have been there too. My sister (currently dealing with an overly anxious young teen) said to me that I didn't have to be a tough parent- I said, "now? no I don't. They are all grown up"..."but don't ever forget that I drove my son to turn himself in to the police and get locked up for 6 months" THAT is a tough parent. It sucks. But it was the right thing to do for both my son and myself.