9 CFR 590.30: At official plants.

(a) Requirements within the scope of the Act with respect to premises, facilities, and operations of any official plant which are in addition to or different than those made under this part may not be imposed by any State or local jurisdiction except that any such jurisdiction may impose recordkeeping and other requirements within the scope of § 590.200, if consistent therewith, with respect to any such plant.

(b) Labeling, packaging, or ingredient requirements in addition to or different than those made under this part, the Federal Food, Drug, and Cosmetic Act and the Fair Packaging and Labeling Act may not be imposed by any State or local jurisdiction with respect to egg products processed at any official plant in accordance with the requirements under this part and such Acts.