Mo. Rev. Stat. § 196.555: The state milk board's right of access.

The state milk board* shall have access to all dairy farms producing manufacturing milk, dairy manufacturing plants and dairy receiving stations; to all equipment; and to all vehicular conveyances used in the production, transportation and manufacture of milk and its products when offered, exposed for sale or sold; and to locations where market sampling, measuring, weighing, or testing is done for the first point of sale.