Supreme Court Hands Monsanto a Legal Win—But the Roundup Cancer Debate Rages On

The Court’s Ruling: States Can’t Force Warnings Beyond EPA’s Approval

The U.S. Supreme Court delivered a sweeping legal victory to Monsanto on June 27, in Monsanto v. Durnell, but it left the scientific question of whether Roundup causes cancer entirely untouched. In a 6–3 decision, Justice Brett Kavanaugh ruled that federal pesticide law preempts state-level lawsuits demanding cancer warnings when the Environmental Protection Agency (EPA) has not required them. The ruling doesn’t declare Roundup safe—it simply bars states from imposing stricter labeling rules than Washington mandates.

Plaintiffs in future lawsuits will now face an uphill battle. The Court’s decision means Monsanto cannot be held liable for failing to warn users of cancer risks if the EPA hasn’t done so itself. But the core conflict—decades of clashing scientific evidence—remains unresolved.

A Divided Science: WHO’s “Probably Carcinogenic” vs. EPA’s “Not Likely”

The World Health Organization’s International Agency for Research on Cancer (IARC) declared glyphosate—the active ingredient in Roundup—”probably carcinogenic to humans” in 2015, citing limited but troubling evidence from animal studies and occupational exposures. The EPA, however, has repeatedly dismissed those concerns, concluding in 2023 that glyphosate is “not likely to be carcinogenic to humans” under normal use.

"It just says states can’t force warnings beyond what the EPA allows."

The split isn’t just ideological. A 2024 meta-analysis in The BMJ found that occupational glyphosate exposure was linked to a higher risk of non-Hodgkin lymphoma, though the study acknowledged methodological limitations. Meanwhile, the EPA’s 2023 review insisted that glyphosate residues in food “are not of concern” for cancer risk.

Billions in Settlements—and a Legal Strategy Shift

The ruling directly targets thousands of pending lawsuits from Roundup users who claim the herbicide caused their non-Hodgkin lymphoma. Before this decision, plaintiffs had won billions in settlements and jury awards by arguing Monsanto failed to warn them of cancer risks. Now, those cases hinge on whether the EPA’s labeling is sufficient—or if federal law truly blocks state warnings.

Legal experts warn the decision could embolden Monsanto to dismiss future lawsuits. “Companies will now have a stronger argument to dismiss lawsuits based on preemption,” said Michael Greve, a University of Chicago Law School professor, in an interview with STAT. “But it doesn’t change the underlying science—or the fact that many users still believe Roundup is dangerous.”

Bayer, which acquired Monsanto, already faces the fallout. In 2025, it settled a large number of Roundup lawsuits, acknowledging that some users developed cancer after exposure. The company insists its products are safe when used as directed—but the Supreme Court’s ruling may now limit its legal exposure in future cases.

Public Trust vs. Regulatory Stance: A Disconnect

A 2025 Pew Research poll revealed a stark divide: a majority of Americans believe glyphosate is harmful to human health, while a minority think it’s safe. The EPA’s stance—reaffirmed in 2023—remains that “the weight of scientific evidence does not support a causal link between glyphosate and cancer.” Yet the agency also acknowledged that some studies suggest potential risks under high-dose or long-term exposure scenarios not covered by typical use.

Advocacy groups like the Environmental Working Group (EWG) see the Court’s ruling as a setback. “This is a victory for Monsanto’s lawyers, not for public health,” said EWG senior scientist Alexis Temkin in a 2026 statement. “The EPA’s approval process is broken—it’s time for an independent review of glyphosate’s risks.”

Where the Fight Moves Next: Regulatory Battles, Not Courtrooms

With the legal path narrowed, the debate shifts to regulatory policy. The EPA’s approval process—and whether it truly protects public health—now stands at the center of the conflict. Consumers are left with mixed advice: follow EPA-approved label instructions, but some health advocates urge minimizing exposure by opting for organic farming or alternative herbicides.

Policymakers face a critical choice: trust the EPA’s risk assessments or demand independent reviews. The Supreme Court’s decision removes one legal avenue for plaintiffs—but it doesn’t erase the underlying questions about glyphosate’s safety, or the public’s right to know about potential risks.