Mass. Gen. Laws ch. 180, § 23

Every such corporation may enter into written agreements with any dairymen for the production of milk under the supervision of such corporation and prescribe in such agreements the conditions under which such milk shall be produced, which, however, shall be approved by the department of public health and shall not fall below the standards of purity and quality for certified milk as fixed by the American Association of Medical Milk Commissions and the standards for milk fixed by law.