I think that learning to set limits and say, "No" is one of the most important things a parent can do. Ultimately, you will need to determine what you are and aren't willing to do with your son, but he is going to have to figure out when he is ready to quit and take recovery seriously. Not giving up on him is important, but you don't have to do things that further his addiction along. For example: he is in jail and probably needs to be. Will he ask you to pay for an attorney or a rehab (often they offer rehab as an alternative to incarceration)? You could find a list of free/low cost legal representation and a list of rehabs that will work with him and then he can make the calls, for example.