Cal. Penal Code § 2717.8

The compensation of prisoners engaged in programs pursuant to contract between the Department of Corrections and joint venture employers for the purpose of conducting programs which use inmate labor shall be comparable to wages paid by the joint venture employer to non-inmate employees performing similar work for that employer. If the joint venture employer does not employ such non-inmate employees in similar work, compensation shall be comparable to wages paid for work of a similar nature in the locality in which the work is to be performed. Such wages shall be subject to deductions, as determined by the Director of Corrections, which shall not, in the aggregate, exceed 80 percent of gross wages and shall be limited to the following: (1) Federal, state, and local taxes. (2) Reasonable charges for room and board, which shall be remitted to the Director of Corrections. (3) Any lawful restitution fine or contributions to any fund established by law to compensate the victims of crime of not more than 20 percent, but not less than 5 percent, of gross wages, which shall be remitted to the Director of Corrections for disbursement. (4) Allocations for support of family pursuant to state statute, court order, or agreement by the prisoner.