7 U.S.C. § 1639i Federal preemption
(a) Definition of foodIn this subchapter, the term “food” has the meaning given the term in section 321 of title 21.
(b) Federal preemptionNo State or a political subdivision of a State may directly or indirectly establish under any authority or continue in effect as to any food or seed in interstate commerce any requirement relating to the labeling of whether a food (including food served in a restaurant or similar establishment) or seed is genetically engineered (which shall include such other similar terms as determined by the Secretary of Agriculture) or was developed or produced using genetic engineering, including any requirement for claims that a food or seed is or contains an ingredient that was developed or produced using genetic engineering.