Some prisons have treatment programs, most do not and few county jails provide treatment and many offenders end up there. The proof or at least the best statistical evidence of the success of such decriminalizing actions is in Portugal. Portugal had a serious problem with substance abuse among its population and over a decade ago decriminalized possession and use of drugs and made treatment programs universally available. The results were a spectacular reduction in drug use, addiction and overdoses. There are numerous articles on the subject for anyone interested.