The Parole Board’s failure to retain a parolee during the 30-day review period provided by Penal Code section 3001, subdivision (a) deprives it of jurisdiction to revoke parole at a later date. Under Penal Code section 3001, the Department of Corrections must discharge a parolee who has been on parole continuously for three years since release from confinement unless in the 37th month the department makes a recommendation to the Parole Board that the parolee remain on parole, and the board also determines there is good cause to retain the parole. Petitioner was released from prison in November 2005. His parole was revoked once in 2007, but that decision was vacated in a habeas action. Then in December 2008, during the 30-day review period contemplated by the statute, another parole violation was charged, but parole was not revoked until February 2009. Petitioner filed the current habeas petition alleging lack of jurisdiction to retain him at that point. The appellate court agreed. Petitioner had been on parole continuously for three years since release from confinement (Nov. 22, 2005 through Nov. 21, 2008). The only revocation during that time was ified by the court. While a parole violation was charged during the 30-day review period, it was not acted upon until after that period had expired. The department needed to have made a recommendation to the board that petitioner be retained, and the board needed to have made a determination of good cause to retain petitioner during the 30-day period. Since these events did not occur during the 30-day review period, petitioner was technically discharged from parole by operation of law at the end of the 30-day review period (Dec. 22, 2008).