Cal. PCC § 20445

If a contribution of labor or of labor and any portion of materials, supplies or equipment is to be made by any local, state or national agency or authority, the contract shall contain a provision that the legislative body may cancel the order for any undelivered materials, supplies or equipment by giving the contractor 24 hours notice of said cancellation, and require the contractor to accept the return of the unused materials and supplies, in which event the contractor will be entitled to compensation for only so much of the materials, supplies and equipment as has been used prior to the giving of such notice. The contract shall also contain a provision that no materials, supplies or equipment shall be delivered until a delivery permit signed by the superintendent of streets has been received by the contractor.