A Missouri jury found Monsanto liable for failing to warn that its Roundup herbicide could cause cancer, even though the product’s labeling had been approved under the Federal Insecticide, Fungicide, and Rodenticide Act. The Supreme Court held that FIFRA expressly preempts a state-law warning claim when liability would require a pesticide label different from or additional to the labeling requirements imposed under federal law. A State may enforce genuinely equivalent federal requirements, but it may not use tort law to compel a cancer warning that federal labeling law does not require. The judgment was reversed and the case remanded.