California Code, Penal Code - PEN § 416

(a) If two or more persons assemble for the purpose of disturbing the public peace, or committing any unlawful act, and do not disperse on being desired or commanded so to do by a public officer, the persons so offending are severally guilty of a misdemeanor.

(b) Any person who, as a result of violating subdivision (a), personally causes damage to real or personal property, which is either publicly or privately owned, shall make restitution for the damage he or she caused, including, but not limited to, the costs of cleaning up, repairing, replacing, or restoring the property.  Any restitution required to be paid pursuant to this subdivision shall be paid directly to the victim.  If the court determines that the defendant is unable to pay restitution, the court shall order the defendant to perform community service, as the court deems appropriate, in lieu of the direct restitution payment.

(c) This section shall not preclude the court from imposing restitution in the form of a penalty assessment pursuant to Section 1464 if the court, in its discretion, deems that additional restitution appropriate.

(d) The burden of proof on the issue of whether any defendant or defendants personally caused any property damage shall rest with the prosecuting agency or claimant.  In no event shall the burden of proof on this issue shift to the defendant or any of several defendants to prove that he or she was not responsible for the property damage.