I believe with a lot of hard work anyone can quit any drug on their own if they work a good program. There is so much help out there now it is almost impossible not it "IF" you really want to quit.
There is a plethora of recovery choices, online support, free support, you name it. But it is not easy, and you have to want it.
Me personally I stopped a bad meth habit, a bad cutting habit, a basically a lifelong eating disoreder purging/starving all on the same day.
I think most would say it was impossibe for me to do on my own, especially considering I was two minutes from suicide. Actually the hospital I went to get help at, said I needed intense in-patient, at the very least, full time day patient or I would die, they also said I needed insurance and/or a lot of money.
I did it without rehab, just used any resource I could find to help me, that I felt did help me in the way I needed. That is what worked for me, not saying it can work for everyone. Just my experience.
I think the most important thing is to keep yourself healthy because that is the only thing we know the truth about and can control.
Here is a huge list of help for him and that may help you as well. http://www.soberrecovery.com/forums/...i-recover.html