Penal Code § 4570.1
CHAPTER 3. Unauthorized Communications With Prisons and Prisoners
Every person who, without permission of the peace officer or corrections officer in charge of any vehicle, bus, van or automobile used for the transportation of prisoners, delivers a written communication to any prisoner or person detained therein, or being escorted to or from that vehicle, or takes from or gives to the prisoner any item, is guilty of a misdemeanor.