Cal. Pen. Code § 1567
When it is necessary to have a person imprisoned in the state prison brought before any court, or a person imprisoned in a county jail brought before a court sitting in another county, an order for that purpose may be made by the court and executed by the sheriff of the county where it is made. The order shall be signed by the judge or magistrate and sealed with the seal of the court, if any. The order shall be to the following effect:
County of ____ (as the case may be).
The people of the State of California to the warden of ____ (or sheriff of ____, as the case may be):
An order having been made this day by me, that A. B. be produced in this court as witness in the case of ____, you are commanded to deliver him or her into the custody of ____.
Dated this ____ day of ____, 19__.
Ca. Pen. Code § 1567