California Code, Food and Agricultural Code (Formerly Agricultural Code) - FAC § 55409

Juice or must used for wine which, as a condition of sale, is required to be pressed or crushed from grapes in the field or at a facility not owned by the purchasing vintner, is a farm product for purposes of this chapter. Juice or must which was not required to be pressed or crushed from grapes as a condition of a sale, and which is stored for the account of the producer who grew the grapes, is not a farm product when it is sold.