California Code, Penal Code - PEN § 11191

(a) Any court or other agency or officer of this state having power to commit or transfer an inmate, as defined in Article II(d) of the Interstate Corrections Compact or of the Western Interstate Corrections Compact, to any institution for confinement may commit or transfer that inmate to any institution within or outside of this state if this state has entered into a contract or contracts for the confinement of inmates in that institution pursuant to Article III of the Interstate Corrections Compact or of the Western Interstate Corrections Compact.

(b) No inmate sentenced under California law may be committed or transferred to an institution outside of this state, unless he or she has executed a written consent to the transfer.  The inmate shall have the right to a private consultation with an attorney of his choice, or with a public defender if the inmate cannot afford counsel, concerning his rights and obligations under this section, and shall be informed of those rights prior to executing the written consent.  At any time more than five years after the transfer, the inmate shall be entitled to revoke his consent and to transfer to an institution in this state.  In such cases, the transfer shall occur within the next 30 days.

(c) This section shall become operative on January 1, 2020.