The short answer is... it depends. The new charge in and of itself is a violation but how the parole board handles the dismissal is up to them. The maximum time they can give you is the remaining portion of your sentence.
I was a probation and parole officer for the State of Missouri before becoming an attorney and in cases where charges were dismissed, it was unlikely that the person was sent back to prison. It will greatly depend on your supervision history, what you are on parole for (current charge) and the recommendation of the PO.
My guess is that if you have been doing well on supervision, haven't tested positive for any controlled substances, and you are reporting consistently, your chances of remaining in the community greatly increase. They chances of success are even greater if you are working, maintain a stable home plan, and have a good rapport with your officer.
In any event, I believe it is a good idea to consult with an experience criminal defense attorney to find representation at your parole violation hearing. Without knowing more, this is the best advice I can give you. Best of luck to you!
If the defendant was on parole at the time he was arrested and charged with a drug offense, that is a violation of the general terms of his parole to remain arrest free and law abiding. I assume those are part of his parole conditions. I don't practice in MO, but it KY the parole officer could take out a PV warrant and arrest the parolee and subject him to an administrative law judge hearing to see if he should be returned to prison being review by the parole board.
The fact that the charge was dismissed is certainly in his favor butis not necessarily dispostive of the issue. He needs to retain a criminal defense attorney to assist him.
The maximum time he is subjected to is the balance of his paroled sentence remaining.
I am trying to give you a general answer to your question. We do not have an attorney-client relationship by this response on the avvo website. I have not been retained to represent you. I am licensed to practice law in Kentucky and in federal court in this state and the Southern District of Indiana. You need to seek legal advice from an attorney licensed to practice in your area..