Surely you know that rescuing him as he leaves jail will only enable his disease to progress.
If you are willing to help, perhaps you can find a long term treatment center and make that your only offer - that he enter the day he is released.
If he doesn't choose treatment then he will need to keep going until he finds his bottom.
I know it is tough to parent a grown addict. My own son is currently in his 10th month at a long term program. He went pretty low before he was willing to go, again. This is his third treatment.
Keep hope alive that your son is ready to change and willling to do whatever necessary to stay sober.
Take care of yourself as you remember how to let go, detach and help.