California Code, Labor Code - LAB § 9102

(a) The owner, manager, or operator of a working warehouse shall secure merchandise stored on shelves higher than 12 feet above the sales floor.  Methods of securing merchandise shall include rails, fencing, netting, security doors, gates, cables, or the binding of items on a pallet into one unit by shrink-wrapping, metal or plastic banding, or by tying items together with a cord.

(b) All working warehouses shall comply with the provisions of this section on or before July 1, 2002.