Cal. Food & Agric. Code § 62663

For purposes of enforcing this chapter, the secretary may investigate any and all transactions between producers and handlers, between nonprofit cooperative associations and producers, and among handlers. For that purpose, the secretary shall have access to, and may enter at all reasonable hours, any place where milk is being stored, bottled, or manufactured and where milk is being bought, sold, or handled, or where the books, papers, records, or documents that relate to those transactions are kept. The secretary may inspect and copy those books, papers, records, or documents at any place within the state.