Bayer Roundup win expected to doom thousands of claims

Bayer AG's success in persuading the U.S. Supreme Court on Thursday that it cannot be held liable for failing to warn consumers about the potential dangers of the Roundup weedkiller will doom many plaintiff claims while forcing their attorneys to adopt new, more challenging legal strategies.

"This is not a silver bullet, but it's as close to it as [Bayer subsidiary] Monsanto could have hoped for," said Adam Zimmerman, a professor at USC Gould School of Law who has been following the Roundup litigation for years.

"It's hard to understate how much of a win this is for Bayer," he added.

The court's 7-2 ruling in a case involving a Missouri gardener, John Durnell, who won a $1.25 million award after contracting non-Hodgkin lymphoma does not squelch all of plaintiff's claims against Bayer over the weedkiller but does knock out a key one.

Justice Brett M. Kavqanugh ruled that the Federal Insecticide, Fungicide and Rodenticide Act, or FIFRA, preempts failure-to-warn claims under state laws. Thousands of lawsuits against Bayer - including in California -- have relied on that claim, which legal experts say make allegations easier to prove.

"Because Durnell's state tort claim would impose a pesticide labeling requirement 'in addition to or different from" the label required by EPA, FIFRA expressly preempts Durnell's claim," Kavanaugh wrote. Monsanto Co. v. Durnell, 2026 DJDAR 5227 (S. Ct., filed April 4, 2025).

Justice Ketanji Brown Jackson, joined by Justice Neil M. Gorsuch, dissented, arguing that the court ruling "ultimately leaves Durnell without a remedy for the significant harms he has suffered."

Bayer stock soared on the ruling, rising 17% during Thursday trading.

Jennifer A. Moore of Moore Law Group PLLC, who helped win a $25 million verdict for plaintiff Edwin Hardeman after the 9th U.S. Circuit Court of Appeals affirmed the outcome, decried Thursday's ruling but said plaintiffs can still bring design defect, general negligence and consumer protection claims.

"What today's decision did was preclude one claim among many claims that we have against companies like Monsanto, who put a harmful product on the market, deceived the American public for decades...resulting in harm to thousands of individuals" Moore said. "Those individuals still have other claims they can bring."

Brent Wisner, managing partner of Wisner Baum LLP who has represented plaintiffs in a number of Roundup cases and won $2.3 billion in jury verdicts, said in a statement that more than 60,000 lawsuits against Bayer are pending.

"This decision is a severe blow to holding corporations accountable," Wisner said. "This is not the outcome we wanted from the Supreme Court, but it means there is more work to be done."

Zimmerman agreed that the court's decision only applied to state failure-to-warn claims, not design defect or other claims, but he estimated that would knock out 30,000 complaints could be dismissed as a result.

He also said failure-to-warn claims are much easier because they require attorneys to establish that Monsanto officials were aware of the dangers of Roundup's active ingredient, glyphosate, but did not let consumers know on a warning label.

Zimmerman added that many design defect claims relied heavily on failure-to-warn claims, making them vulnerable to dismissal. "It's just a much harder case," he said.

The Bayer argument for preemption had been unsuccessful for years, including rejection by the 9th U.S. Circuit Court of Appeals, but the company caught a break when the 3rd U.S. Circuit Court of Appeals became the first federal appellate court in 2024 to rule for the company's argument - creating a circuit split.

The Supreme Court, which previously rejected a bid to review the 9th Circuit decision, asked the Trump administration to file a brief, which it did in Bayer's favor.

Thursday's ruling could have impacts that extend beyond the Roundup cases, according to Dennis E. Raglin, a partner with Carlton Fields LLP who represents defendants in cases involving California's Proposition 65, which requires warnings when residents are exposed to certain chemicals.

He said several courts have now struck down labeling requirements either on preemption or First Amendment grounds.

"This is definitely not the last challenge we're going to have given that so many different chemicals are regulated by federal agencies," Raglin said. "It doesn't spell the death knell for Prop. 65 but ... it gives defendants the wind at their backs."