US Supreme Court Split Over Bayer’s Bid to Block Roundup Cancer Lawsuits

The US Supreme Court appeared divided over Bayer AG’s effort to shut down thousands of lawsuits accusing the company of failing to warn users that the active ingredient in its Roundup weedkiller causes cancer.

The justices heard arguments in the German drug-making and crop science company’s appeal of a jury verdict in a Missouri state court awarding $1.25 million to a man named John Durnell, who said he was diagnosed with non-Hodgkin lymphoma after years of exposure to glyphosate in Roundup.

Paul Clement, arguing for Bayer, told the justices that federal law governing pesticides should prevent failure-to-warn claims like Durnell’s, brought under state law, from proceeding in court.

Bayer has said the US Environmental Protection Agency (EPA) has repeatedly found that glyphosate does not cause cancer and has approved product labels without any warning requirement.

“A Missouri jury imposed a cancer-warning requirement that the EPA does not require. That additional requirement is pre-empted,” Mr Clement said.

He warned against allowing a patchwork of standards across the United States.

“Congress plainly wanted uniformity when it came to the safety warnings on a pesticide’s label. Ignoring Congress’ clear direction here would open the door for crippling liability and undermine the interests of farmers who depend on federally registered pesticides for their livelihood,” he said.

More than 100,000 plaintiffs have filed cases in US state and federal courts alleging a cancer link, according to Bayer. The company has said a Supreme Court ruling in its favour should largely bring the Roundup litigation to an end.

A US law known as the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) governs the sale and labelling of pesticides and bars states from imposing differing or additional requirements. It prohibits pesticides that are “misbranded”, including labels that fail to carry adequate warnings to protect health and the environment.

Conservative Justice Neil Gorsuch questioned Mr Clement on why state court lawsuits are necessarily at odds with the federal regulatory scheme.

“If the EPA can bring a claim against you for misbranding and seek criminal and civil penalties despite a properly registered item, how would it be inconsistent with FIFRA to allow state tort suits to do the same thing?” he asked.

The administration of US President Donald Trump sided with Bayer in the case.

Chief Justice John Roberts asked Sarah Harris, a Justice Department lawyer arguing for the administration, whether states have any legal recourse if new evidence of harm emerges while federal regulators consider updated guidance.

Ms Harris stressed the risks of departing from a national standard.

“If you had 50 different states that are just jumping the gun — Iowa says maybe this causes cancer, California says it absolutely causes cancer, some other state says this doesn’t cause cancer at all, so put that on your label too — it completely undermines the uniformity of the labelling,” she said.

“I appreciate that,” Chief Justice Roberts replied. “On the other hand, if it turns out they were right, it might have been good if they had an opportunity to do something to call this danger to the attention of the people while the federal government was going through its process.”

Conservative Justice Brett Kavanaugh and liberal Justice Elena Kagan both appeared concerned about the implications of a fragmented regulatory system.

“You have a pre-emption provision that’s clearly designed to achieve uniformity in labelling,” Ms Kagan told Ashley Keller, a lawyer for Durnell. “What uniformity would your regime achieve?”

She added: “It seems here as though there’s a pretty big delegation of power to the EPA to figure all these matters out.”

A Proposed Settlement

Bayer acquired Roundup as part of its $63 billion purchase of agrochemical company Monsanto in 2018. The wave of litigation prompted Bayer to remove glyphosate from its consumer version of Roundup, and the company has warned the lawsuits could threaten its ability to supply the herbicide to farmers.

Facing billions of dollars in potential liability, Bayer announced in February a proposed $7.25 billion settlement to resolve tens of thousands of current and future claims. The settlement would not affect cases under appeal or those outside the agreement, the company said, estimating those at nearly $1 billion.

Durnell was diagnosed with a rare and often aggressive form of non-Hodgkin lymphoma, a cancer affecting white blood cells, and attributed the disease to his exposure to Roundup from 1996. For about 20 years, he worked as the “spray man” for a neighbourhood association in St Louis, treating weeds in local parks without protective equipment, according to court filings.

A jury found in Durnell’s favour in 2023, and a state appeals court upheld the verdict in 2025.

The Supreme Court is expected to deliver its ruling by the end of June.

 

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