There was a time when a convict released on parole wasn’t allowed to imbibe in alcohol, and of course no drugs, and if discovered to have done so, would have violated his parole, and be sent back to prison. I know parole requirements can include them have to attend mandatory drug and alcohol rehab programs, so I’m assuming there may still be restrictions on their drinking. Regarding their use of drugs, they’d probably have to do a piss test every time they met their parole officer. We tested inmates urine regularly in prison. It was done randomly, and also when there was suspicion of use.
But... this is a time when felons EN MASSE were released from prison to "keep them from getting infected by the coronavirus". Do you think there was any instruction given to them or that all of them were assigned parole officers ?
I'm not saying it couldn't be done. I'm asking if it is even practical.