Cal. Penal Code § 1555.1

Any person arrested in this state charged with having committed any crime in another state or alleged to have escaped from confinement, or broken the terms of his or her bail, probation or parole may waive the issuance and service of the Governor’s warrant provided for in this chapter and all other procedure incidental to extradition proceedings, by subscribing in the presence of a magistrate within this state a writing which states that he or she consents to return to the demanding state; provided, however, that before such waiver shall be subscribed by such person, the magistrate shall inform him or her of his or her rights to require the issuance and service of a warrant of extradition as provided in this chapter. If such waiver is executed, it shall forthwith be forwarded to the office of the Governor of this state, and filed therein. The magistrate shall remand the person to custody without bail, unless otherwise stipulated by the district attorney with the concurrence of the other state, and shall direct the officer having such person in custody to deliver such person forthwith to the duly authorized agent of the demanding state, and shall deliver to such agent a copy of such waiver. Nothing in this section shall be deemed to limit the rights of the accused person to return voluntarily and without formality to the demanding state, provided that state consents, nor shall this procedure of waiver be deemed to be an exclusive procedure or to limit the powers, rights or duties of the officers of the demanding state or of this state.