Cal. Food & Agric. Code § 34591

Except as otherwise provided in this article, it is unlawful for any person to sell or otherwise dispose of any market milk, skim milk, flavored milk, flavored dairy drink, buttermilk, or cultured buttermilk to the retail trade, unless the product is contained in a standard milk bottle or in a single service container which has been mechanically filled and capped or sealed in a milkroom which is properly designed and equipped as approved by the director. The pouring lip of standard milk bottles used to package market milk and milk products sold at retail shall be covered at the time of capping or closure to at least its largest diameter by the cap or cover. A single service container shall meet the specifications of the United States Public Health Service Grade A Pasteurized Milk Ordinance Recommendations.