California Code, Vehicle Code - VEH § 23115

(a) No vehicle transporting garbage, swill, used cans or bottles, wastepapers, waste cardboard, ashes, refuse, trash, or rubbish, or any noisome, nauseous, or offensive matter, or anything being transported for disposal or recycling shall be driven or moved upon any highway unless the load is totally covered in a manner that will prevent the load or any part of the load from spilling or falling from the vehicle.

(b) Subdivision (a) does not prohibit a rubbish vehicle from being without cover while in the process of acquiring its load if no law, administrative regulation, or local ordinance requires that it be covered in those circumstances.

(c) Vehicles transporting wastepaper, waste cardboard, or used cans or bottles, are in compliance with subdivision (a) if appropriate binders including, but not limited to, bands, wires, straps, or netting are used to prevent the load, or any part of the load, from spilling or falling from the vehicle.

(d) This section does not apply to any vehicle engaged in transporting wet waste fruit or vegetable matter, or waste products to or from a food processing establishment.