Cal. Civ. Proc. Code § 1603

The State hereby undertakes to hold the United States harmless against any claim concerning property delivered to the custody of the State in accordance with the provisions of this chapter. In the event an action or proceeding on such claim is brought against the United States the Attorney General shall intervene therein. The State consents to suit by such claimant in such contingency and any defense in favor of the United States shall be available to and urged by the State.