Supreme Court justices on Monday appeared skeptical of Monsanto’s argument that federal law prevents state courts from holding the company financially responsible for failing to warn consumers about the risk of cancer from its popular Roundup weedkiller.
During oral arguments, Monsanto and the Trump administration faced questions about their position that EPA should have the final say on what warnings pesticides and herbicides can carry — even in light of new information about a product’s potential hazards.
Chief Justice John Roberts asked Paul Clement, the attorney representing Monsanto, why states couldn’t also hold chemical manufacturers’ feet to the fire when they’ve made a determination that a product poses risk to their residents.
“It’s not necessarily the case that they’re doing something inconsistent with what the EPA would do,” said Roberts, who is often a swing vote in Supreme Court cases. “It’s simply the fact that they’re responsive to the new information more quickly than the federal government.”
At the heart of the case, Monsanto v. Durnell, is whether a Missouri jury — and other state courts across the country — correctly awarded verdicts exceeding $1 million to compensate longtime Roundup users after they developed non-Hodgkin lymphoma.
Roundup users have argued in thousands of lawsuits that the company failed to warn customers about the risks of glyphosate, the herbicide’s key ingredient. But EPA, the agency responsible for registering pesticides and herbicides, has determined that glyphosate is not a likely carcinogen.
Monsanto’s attorneys argue that adding a warning to Roundup’s label would conflict with EPA’s findings and that different state warnings about the product would violate uniformity requirements under the Federal Insecticide, Fungicide and Rodenticide Act.
The state litigation is a major liability for Monsanto and its owner, German pharmaceutical company Bayer, which has entered a $7.25 billion settlement to resolve Roundup cancer claims.
Clement — founder of the boutique law firm Clement & Murphy and former U.S. solicitor general — argued Monday on behalf of Monsanto that there are other options for states to push an unresponsive EPA to act on new scientific information, such as pursuing a petition to cancel a product’s registration.
Justice Brett Kavanaugh, another swing vote on the high court, appeared more sympathetic to Monsanto’s claims.
“I think you’re saying that EPA can change requirements going forward, but if it tries to say you are misbranding [a product] when you do what they told you to do, in a sense they’re penalizing you retroactively,” Kavanaugh said.
Clement said he thought the retroactivity framing was a helpful way to look at the case.
“If you look at the statutory scheme, the real way you change warnings or take a pesticide off the market is through the cancellation proceedings,” he said.
Appearing alongside Monsanto in the case, Principal Deputy Solicitor General Sarah Harris argued for the Trump administration that states can restrict pesticide use within their borders but can’t impose labeling requirements.
Justice Neil Gorsuch pushed back against the claim.
“Because the greater power exists,” he asked, “why doesn’t the lesser power?”
An attorney for John Durnell, the Missouri resident who secured one of the verdicts against Monsanto in state court, faced fewer questions from the justices.
Justice Clarence Thomas asked the lawyer, Ashley Keller, a founding partner at the law firm Keller Postman, to flesh out his argument that the demise of the Chevron doctrine has undermined Monsanto’s case.
Keller pointed back to the Supreme Court’s 2024 ruling in Loper Bright v. Raimondo, which overturned the 40-year-old principle of Chevron deference, which said judges should generally give agencies like EPA leeway on their reasonable interpretations of ambiguous federal laws.
Under Loper Bright, it is now up to courts to determine who has the best reading of laws like FIFRA that shape federal regulations.
If EPA had created a rule that said Roundup is safe, in the Chevron regime, “you could engage in that fiction that Congress delegated that power to EPA,” Keller said to the justices.
“In the new Loper Bright regime,” he continued, “you would say, ‘Point to the text.’”
Justices Samuel Alito and Elena Kagan asked if Keller had properly applied Loper Bright. Altio said the case was about the separation of powers between two branches of government, the executive and the judiciary. Kagan said the decision did not prevent Congress from handing off power to agencies like EPA.
Keller agreed with Kagan, but said Congress did not broadly delegate to EPA blanket authority to decide when a product is or is not misbranded.
“Things slip through the cracks,” Keller said.
Outside the court
While the justices parsed the arguments from Monsanto and its challengers, roughly 200 people gathered in front of the Supreme Court to oppose the pesticide manufacturer’s position and the Trump administration’s support of it.
“Stop the poison now!” protestors chanted.
“Make Monsanto pay,” read one sign. “Your poison, your problem,” read another.
The rally, dubbed “People vs. Poison,” included speeches from current and former members of Congress, high-profile Make America Healthy Again influencers and anti-pesticides environmental advocates.
“The federal government, and especially the executive branch, do not have this power to issue get-out-of-court free cards. And we’re going to fight it,” Rep. Thomas Massie (R-Ky.) said in his address to the crowd.
The Trump administration has filed multiple amicus briefs siding with Monsanto, and President Donald Trump signed an executive order in February identifying threatened glyphosate supply as a national security risk. The administration’s pro-industry position has ruffled feathers with those aligned with Health Secretary Robert F. Kennedy Jr.’s anti-corporate MAHA movement.
“We are talking about a system where corporations farm us for profit while fueling a staggering disease and illness epidemic,” said Kelly Ryerson, a MAHA influencer known online as “Glyphosate Girl.” “A government that shields corporations from the people does not serve the public. It is captured.”
Monsanto said in a Monday statement that it appreciated the Supreme Court’s attention to the conflict.
“Companies should not be punished under state law for complying with federal label requirements,” the company said in a statement. “The security and affordability of the nation’s food supply depend on farmers’ and manufacturers’ ability to rely on the science-based judgments of federal regulators. A favorable ruling by the Supreme Court would provide essential regulatory clarity for companies who seek to bring currently approved and new products to market, addressing their ability to serve U.S. farmers and consumers.”
The Supreme Court is expected to issue its decision in Monsanto v. Durnell by early summer.
Rylan DiGiacomo-Rapp contributed to this report.
