on parole
Released earlier from prison than one's sentence had mandated on condition of conforming to a set of specific legal requirements. You're on parole, Dan—if you get caught stealing, they'll send you straight back to prison! No thanks, man, I'm on parole—I have to pass a drug test with my parole officer every week.
(out) on parole
out of prison, conditionally, before one's total sentence is served. Bob was caught using drugs while out on parole and was sent back to prison. He has to be careful and obey the law because he is out on parole.