The Supreme Court Case That Could Reshape Mass Tort Litigation — Monsanto v. Durnell Heads to Oral Arguments

On April 1, 2026, a coalition of 18 attorneys general filed an amicus brief urging the U.S. Supreme Court to reject Monsanto's argument that federal pesticide law preempts state failure-to-warn claims — setting the stage for what may be the most consequential mass tort ruling in a decade. Oral arguments in Monsanto Co. v. Durnell (No. 24-1068) are scheduled for April 27, with a decision expected by late June.

The case arrives as Bayer — which acquired Monsanto for $63 billion in 2018 — has already spent over $16 billion defending and settling Roundup claims, and as a separate $7.25 billion class settlement awaits final approval in Missouri state court. A ruling for Monsanto would not just affect Roundup litigation — it could set precedent limiting failure-to-warn claims for every federally regulated product in the country.

The Case: A Missouri Farmer and a $1.25 Million Verdict

John Durnell used Roundup on his Missouri property for two decades before being diagnosed with non-Hodgkin lymphoma. A Missouri jury awarded him $1.25 million in compensatory damages on a strict liability failure-to-warn theory — finding that Monsanto failed to warn users that Roundup's active ingredient, glyphosate, could cause cancer.

The Missouri Court of Appeals affirmed the verdict. The Supreme Court granted certiorari in January 2026 on a narrow question: whether the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) preempts a state-law failure-to-warn claim where the EPA has not required the warning.

The Legal Battle: Can States Require Warnings the EPA Doesn't?

FIFRA governs the registration and labeling of pesticides in the United States. Manufacturers cannot change EPA-approved labels without agency approval. Monsanto argues this creates an impossible compliance problem: if a state jury finds the company should have warned about cancer, but the EPA has never required such a warning, the manufacturer is caught between conflicting federal and state requirements.

The plaintiff's position — supported by the 18-AG coalition — is that FIFRA does not preempt state failure-to-warn claims. They point to the Supreme Court's own 2005 precedent in Bates v. Dow Agrosciences, where a 7-2 majority held that FIFRA's preemption clause applies only to state requirements that are not "equivalent to, and fully consistent with" FIFRA's own standards. The Bates Court explicitly rejected the argument that any claim which might induce a label change is automatically preempted.

Monsanto's Argument

Monsanto contends that Bates left open the specific question of what happens when the EPA has affirmatively considered and declined to require a warning. The company argues that EPA's repeated conclusion that glyphosate is "not likely to be carcinogenic to humans" means a state-law claim demanding a cancer warning directly conflicts with the federal regulatory scheme. The Solicitor General filed a brief in December 2025 supporting Monsanto's position — a significant signal that the federal government views FIFRA as preemptive in this context.

The Opposition

The 18-AG coalition — representing Arizona, California, Colorado, Delaware, D.C., Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, and Wisconsin — argues that state failure-to-warn claims are essential gap-filling tools for consumer protection. Their brief contends that manufacturers can comply with both state and federal law simultaneously, and that Bates already resolved this issue.

Over 200 environmental and health organizations filed a separate brief arguing that Monsanto's failure-to-warn liability should stand. On the other side, a coalition of states led by agricultural-economy interests filed supporting Monsanto's preemption argument.

What's at Stake — Far Beyond Roundup

The Roundup Impact

Approximately 65,000 active Roundup claims remain pending, including those covered by the $7.25 billion class settlement that received preliminary approval on March 4, 2026. The settlement's opt-out deadline is June 4 — potentially before the SCOTUS decision arrives. Firms advising clients on whether to opt out must weigh the risk that a pro-Monsanto ruling could eliminate the legal theory underlying individual claims.

The Broader Precedent

Legal analysts warn that a broad ruling for Monsanto could extend well beyond pesticides. Any manufacturer of a federally regulated product — pharmaceuticals, medical devices, food additives, chemicals — could argue that federal agency approval preempts state failure-to-warn claims. As the 18-AG brief argues, this would fundamentally shift the balance between federal regulation and state consumer protection.

Historical Context: $16 Billion and Counting

Bayer's Roundup litigation has produced some of the largest verdicts in mass tort history:

• Johnson v. Monsanto (2018): $289 million jury verdict (reduced to $20.5 million on appeal) — the first Roundup cancer trial
• Pilliod v. Monsanto (2019): $2.055 billion jury verdict (reduced to $87 million on appeal)
• Hardeman v. Monsanto (2019): $80.3 million verdict (reduced to $25.3 million) — SCOTUS denied cert in 2022

More than 170,000 Roundup lawsuits have been filed since 2018, with Bayer paying approximately $11 billion in settlements and spending over $16 billion total on litigation costs. The Durnell case gives the Court an opportunity to address the preemption question it sidestepped when it declined to hear Hardeman.

What Firms Should Watch

The Bottom Line

Monsanto v. Durnell is not just a Roundup case — it is a test of whether federal regulatory approval can shield manufacturers from state-law accountability. The 18-AG coalition, the Solicitor General's opposing brief, and the 200+ organizations weighing in reflect the stakes. For plaintiff firms handling Roundup cases, the next 90 days require careful strategic planning around the opt-out deadline and settlement terms. For the broader mass tort bar, this decision could define the boundaries of failure-to-warn litigation for a generation.

Medical records remain the foundation of every Roundup claim — documented non-Hodgkin lymphoma diagnosis, oncology treatment history, and evidence of glyphosate exposure. Regardless of the SCOTUS outcome, firms with complete medical evidence are best positioned to maximize recovery for their clients.

Sources: SCOTUSblog, California AG, Illinois AG, Maryland AG, JD Supra, Bayer, BeyondPesticides. Verdict reduction amounts from court records and NPR reporting.