Supreme Court Blocks State Cancer Lawsuits Against Monsanto

Federal Authority Trumps State Consumer Protection in Landmark Pesticide Case

Monsanto has long argued that states cannot hold manufacturers liable for failing to warn consumers about cancer risks if the U.S. Environmental Protection Agency approves a pesticide label without a cancer warning. The U.S. Supreme Court agreed in a ruling issued on June 25, 2026, though some members of Congress are taking steps to override that decision. The Supreme Court’s ruling effectively shields manufacturers from state-level liability claims when federal regulators have not mandated warnings.

The decision represents a significant victory for Bayer, the German chemical giant that now owns Monsanto, despite the company having paid out over $10 billion to settle approximately 100,000 claims from people who said their health was harmed after exposure to Roundup. The ruling hinges on a federal law passed in 1947 and significantly amended in 1972, the Federal Insecticide, Fungicide, and Rodenticide Act, which bars states from imposing labeling requirements beyond what the federal government has approved.

EPA Repeatedly Found No Human Cancer Risk

Between 2009 and 2019, the EPA repeatedly concluded there is no evidence that glyphosate causes cancer in humans. The agency has therefore allowed glyphosate-based weed killers, including Monsanto’s Roundup, to remain on the market without a cancer warning on its label. While the law was originally administered by the U.S. Department of Agriculture, today the Environmental Protection Agency regulates the registration, use, and sale of pesticides in the United States.

Companies that wish to sell pesticides must demonstrate that their products will not cause unreasonable adverse effects. This federal regulatory framework creates a uniform national standard for pesticide labeling, which the Supreme Court has now ruled takes precedence over state-level consumer protection laws. The tension between federal regulatory approval and state-level consumer protection laws represents a fundamental conflict in American federalism.

International Health Agency Reached Different Conclusion

The EPA’s assessment stands in stark contrast to a 2015 report from the International Agency for Research on Cancer, a branch of the World Health Organization. That report classified glyphosate as “probably carcinogenic to humans” based on “limited” evidence of cancer in humans from real-world exposure and “sufficient” evidence of cancer in experimental animals. A 2025 study produced similar findings in laboratory rats, adding to the body of experimental evidence suggesting potential cancer risks.

The scientific community remains divided on glyphosate’s carcinogenic potential. While the EPA has consistently found no human cancer risk, the World Health Organization’s cancer research agency reached a different conclusion. This divergence highlights the complexity of cancer risk assessment. The assessment involves evaluating exposure levels, duration, and biological mechanisms across diverse populations and experimental conditions.

Hardeman Case Set Precedent for Successful Claims

Several U.S. lawsuits have used the 2015 report to win legal cases claiming that Monsanto failed to warn consumers of the chemical’s dangers. One of the first, Hardeman v. Monsanto Co., ended in a $80 million verdict against Monsanto in 2019. The jury found that Edwin Hardeman, a California man who used the weed killer on his properties, had proved that Roundup had caused his cancer and that Monsanto had failed to warn consumers of the dangers of its product.

“Edwin Hardeman proved that Roundup had caused his cancer and that Monsanto had failed to warn consumers of the dangers of its product,” the jury found in its verdict.

That finding was upheld on appeal, establishing a legal precedent that encouraged thousands of additional lawsuits. The success of the Hardeman case demonstrated that juries could be persuaded by the international cancer research findings, even when federal regulators maintained that the product was safe. The verdict opened the floodgates for similar claims across the country, ultimately leading to the massive settlement that Bayer negotiated to resolve the litigation.

Congressional Response May Override Court Decision

In the years since the Hardeman verdict, Monsanto, now owned by German chemical giant Bayer, has paid out over $10 billion to settle about 100,000 claims from people who said their health was harmed after they were exposed to Roundup. Despite these massive settlements, Monsanto continues to maintain that federal law preempts state liability claims. The Supreme Court’s recent ruling validates this legal position, potentially closing the door on future state-based litigation.

However, some members of Congress are taking steps to override the Supreme Court ruling through new legislation. This congressional response reflects ongoing concerns about consumer protection and the adequacy of federal pesticide regulation. Lawmakers who support overriding the decision argue that states should retain the authority to protect their citizens through stronger warning requirements and liability standards, even when federal agencies have approved products for sale.

Implications for Future Pesticide Regulation

The Supreme Court’s decision extends beyond Roundup to affect how all pesticide manufacturers navigate state and federal regulatory landscapes. The ruling establishes that EPA approval effectively creates a legal shield against state-level failure-to-warn claims, regardless of scientific debate or international health findings. This precedent may embolden manufacturers to resist state-specific labeling requirements for other potentially hazardous agricultural chemicals.

The gap between experimental findings and real-world risk assessment creates ongoing uncertainty for consumers, farmers, and policymakers alike. While laboratory studies and international health agencies suggest potential cancer risks, federal regulators have concluded that real-world exposure levels do not pose unreasonable dangers. This regulatory determination now carries the weight of Supreme Court endorsement, making it significantly harder for individuals to seek compensation through state court systems when they believe pesticide exposure has caused them harm.