Cal. Food & Agric. Code § 74652.5

Unless otherwise exempted by this chapter, the assessment provided for in this article shall be levied on vintners and vintners who are also producers who engage in the act of processing winegrapes into must for the purpose of making grape juice, grape concentrate, wine, or products thereof, including high proof or brandy or processing field crushed must for the purpose of making grape juice, grape concentrate, wine, or products thereof, including high proof or brandy.