California Code, Business and Professions Code - BPC § 12730

(a) Except as provided in subdivision (a) or (b) of Section 12701 or this section, farm products sold by bulk weight or delivered to a processing or conditioning establishment for processing, conditioning, or sale, shall be weighed by a weighmaster, and a weighmaster certificate of the weight shall be issued to the producer with a duplicate copy issued to the buyer, conditioner, or processor.

(b) When the processing or conditioning charges or purchase is based on the bulk weight of the finished product, the finished product shall also be weighed by a weighmaster, and a second weighmaster certificate shall be issued to the producer with a duplicate copy issued to the buyer, conditioner, or processor.

(c) A producer whose product is delivered, but is not sold, to a processor or conditioner for processing or conditioning, may waive, in writing, his or her right to have the product weighed when the processing or conditioning establishment is operated by a producer of farm products and the processing or conditioning is incidental to the production of farm products.  As used in this subdivision, “incidental” means that the income derived from the processing or conditioning operation represents not more than 25 percent of the total income of the producer operating the processing or conditioning establishment.

(d) This section does not apply to any nonprofit cooperative association that is organized and operating pursuant to Chapter 1 (commencing with Section 54001) of Division 20 of the Food and Agricultural Code, except as to that portion of activities that involves the handling or dealing in any farm product of any nonmember of the nonprofit cooperative association.

(e) Subdivision (a), as it applies to tree nuts delivered for processing or conditioning, does not apply to tree nut hullers and shellers, if there is a written contract which waives the producer's right to have the unprocessed or unconditioned product weighed.  Notwithstanding the waiver, the finished product shall be weighed by a weighmaster and a weighmaster certificate shall be issued to the grower, with a duplicate copy issued to the buyer, conditioner, or processor.

(f) The term “farm products” includes all agricultural, horticultural, viticultural, and vegetable products of the soil, flaxseed, and cottonseed, but does not include timber, timber products, milk, and milk products.