California Code, Penal Code - PEN § 2761

The Director of Corrections shall determine which prisoners shall be eligible for employment by the Department of Transportation in the improvement and maintenance of state highways, and shall establish lists of prisoners eligible for such employment.  Upon the requisition of said department, the Director of Corrections shall send to the place and at the time designated the number of prisoners requisitioned or such number thereof as have been determined to be eligible for such employment and are available.

The director may return to prison any prisoner transferred to camp pursuant to this section, when the need for such prisoner's labor has ceased or when the prisoner is guilty of any violation of the rules and regulations of the prison or camp.