7 U.S. Code § 7756 - Preemption

(a) Regulation of foreign commerceNo State or political subdivision of a State may regulate in foreign commerce any article, means of conveyance, plant,biological control organism, plant pest, noxious weed, or plant product in order—
(1)
to control a plant pest or noxious weed;
(2)
to eradicate a plant pest or noxious weed; or
(3)
prevent the introduction or dissemination of a biological control organism, plant pest, or noxious weed.
(b) Regulation of interstate commerce
(1) In general

Except as provided in paragraph (2), no State or political subdivision of a State may regulate the movement in interstate commerce of any article, means of conveyance, plant,biological control organism, plant pest, noxious weed, or plant product in order to control a plant pest or noxious weed, eradicate a plant pest or noxious weed, or prevent the introduction or dissemination of a biological control organism, plant pest, or noxious weed, if the Secretary has issued a regulation or order to prevent the dissemination of the biological control organism, plant pest, or noxious weed within the United States.

(2) Exceptions
(A) Regulations consistent with Federal regulations

A State or a political subdivision of a State may impose prohibitions or restrictions upon the movement in interstate commerce of articles, means of conveyance, plants,biological control organisms, plant pests, noxious weeds, or plant products that are consistent with and do not exceed the regulations or orders issued by the Secretary.

(B) Special need

A State or political subdivision of a State may impose prohibitions or restrictions upon the movement in interstate commerce of articles, means of conveyance, plants, plant products,biological control organisms, plant pests, or noxious weeds that are in addition to the prohibitions or restrictions imposed by the Secretary, if the State or political subdivision of a State demonstrates to the Secretary and the Secretary finds that there is a special need for additional prohibitions or restrictions based on sound scientific data or a thorough risk assessment.

(Pub. L. 106–224, title IV, § 436, June 20, 2000, 114 Stat. 453.)
Transfer of Functions

For transfer of functions of the Secretary of Agriculture relating to agricultural import and entry inspection activities under this chapter to the Secretary of Homeland Security, and for treatment of related references, see sections 231, 551(d), 552(d), and 557 of Title 6, Domestic Security, and the Department of Homeland Security Reorganization Plan of November 25, 2002, as modified, set out as a note under section 542 of Title 6.