The labels on the plastic containers would need to comply with the Fair Packaging and Labeling Act (FPLA) of 1967, which prohibits unfair or deceptive packaging and labeling. The statute also specifies types of measurements that should be used when the label of a container references the container's capacity (see Title 16 of the Code of Federal Regulations (C.F.R.) Section 500.16(b)(1)). While regulations at the national level do not specifically address the volume identification markings on these products, you would need to comply with any weights and measures laws of individual states where the product is sold. In addition, retailers that sell the products may have specific requirements.

Concerning your second question, reusable plastic containers would fall under the "housewares exemption," which exempts substances used in contact with food as part of a "houseware" product from the requirement of premarket clearance by the U.S. Food and Drug Administration (FDA) as a food additive. A houseware is generally considered to be an article that is sold without food for use by a consumer (and, in some circumstances, a commercial establishment, such as a restaurant) to hold, prepare or serve food. Although, housewares are exempt from premarket notification, they not exempt from the general safety provisions of the Federal Food, Drug, and Cosmetic Act (see Section 402(a)(1)). Therefore, it remains the responsibility of producers of housewares to ensure that their products are suitable for use with food and will not create a health hazard under the intended conditions of use.