Pretty much everyone who doesn't have a previous conviction has that opportunity. It more so depends on the state you in. They introduced that into legislation because back in the 80s during the crack epidemic, the prison population exploded because of the harsh drug laws (crazy times back then but locking addicts up isnt the answer).
Back then, first time offense and you WOULD see prison time and not just one year either. Today, nowadays, they give u a chance to straighten yourself out through drug court. This second chance is better than getting sentenced to prison on ur first drug offense, but considering relapse rates for schedule 1 drugs are over 50%, over 50% will violate probation/parole and be sentenced for the previous charge and convicted for whatever they did to violate probation.
Nevertheless 50% when talking about millions of ppl charged for possession of drugs does make a difference. For the longest, private prisons did not want these type of laws introduced. The more ppl locked up the more money they make, especially since drug offenders are the easiest to lock up, non-violent offender, guaranteed conviction with evidence, high relapse rate and will have a felony record so the chances of you ending back locked up are much higher.
The system is designed to f*ck u, dont forget it.