7 U.S.C. § 7756 — Preemption

(a) Regulation of foreign commerce: No state or local government can regulate plants, plant products, pests, noxious weeds, biological control organisms, or related items moving in foreign trade in order to control, eradicate, or prevent the spread of a pest or weed. That power belongs to the federal government alone. (b) Regulation of interstate commerce: (1) In general: Once the Secretary has issued a regulation or order to stop a pest, weed, or biological control organism from spreading within the U.S., states generally cannot make their own rules regulating interstate movement of related items for that purpose. (2) Exceptions: (A) A state can impose rules that match and do not go beyond the Secretary's regulations. (B) A state can impose extra rules beyond the Secretary's if it proves to the Secretary — using sound scientific data or a thorough risk assessment — that it has a special need for them, and the Secretary agrees.