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The Supreme Court hearing on glyphosate unfolded Monday with sharp ideological divides, as justices wrestled with whether Bayer can be sued for failing to warn consumers that its Roundup weedkiller may cause cancer—a ruling that could either unlock or shut down thousands of lawsuits worth billions.

At the center of the case is a clash between federal pesticide regulation and state product liability laws, with the outcome poised to reshape how far companies must go in warning consumers about potential health risks.

Federal approval vs. state lawsuits

The Environmental Protection Agency, which oversees pesticide safety, has not concluded that glyphosate—the active ingredient in Roundup—poses a cancer risk. It does not require a cancer warning on product labels.

That regulatory stance is now being tested against claims from individuals who say state laws should still allow them to sue if they believe they were harmed.

Justice Brett Kavanaugh pressed the issue of consistency, questioning whether allowing different state requirements would undermine national uniformity in labeling rules.

Chief Justice John Roberts, however, explored whether state lawsuits could serve as a faster response system when new safety information emerges, potentially filling gaps left by slower federal reviews.

Government and Bayer defend federal authority

The Trump administration is backing Bayer, which acquired Roundup maker Monsanto in 2018. Government attorneys argued that federal law requires manufacturers to follow EPA-approved labels, which already reflect safety determinations.

Sarah Harris of the Justice Department told the court that pesticides are only registered after federal review confirms their labels are adequate to protect public health.

Bayer’s legal team argued that allowing state-level lawsuits would create inconsistent rules that could expose companies to liability in some states but not others.

Attorney Paul Clement said Congress intended uniform national standards, warning that fragmented liability rules could destabilize the agricultural industry.

Cancer claims and jury verdicts fuel dispute

Roundup, introduced in the 1970s, became one of the most widely used herbicides in the United States, especially in agriculture.

Litigation surged after a 2015 World Health Organization agency classified glyphosate as “probably carcinogenic to humans,” a conclusion Bayer disputes.

One plaintiff, John Durnell, who used Roundup for decades in St. Louis, said the chemical caused his non-Hodgkin lymphoma. A jury awarded him $1.25 million in 2023, one of many verdicts against Monsanto.

Bayer’s attorneys argue that the EPA has repeatedly reviewed and rejected the need for a cancer warning label.

Debate over regulatory limits and accountability

Plaintiffs’ attorney Ashley Keller argued that federal law does not prevent companies from adding stronger warnings voluntarily, insisting that EPA approval should not act as legal immunity.

He also questioned the reliability of federal oversight, noting that regulatory decisions can lag behind emerging science.

The EPA is required to conduct safety reviews every 15 years, but the latest review of glyphosate has been delayed after a federal court ruled the agency did not fully assess cancer risks.

Broader legal and political stakes

The case intersects with a proposed $7.25 billion class action settlement that could resolve many ongoing lawsuits, regardless of the Supreme Court’s decision.

Bayer is also seeking legislative protections to limit future liability, warning that continued litigation could threaten its ability to sell glyphosate to U.S. farmers.

Agricultural groups have cautioned that removing the product could severely disrupt food production systems across the country.

Public pressure outside the court

Outside the Supreme Court, protestors including retirees Linda and Jon Martin criticized Bayer’s push for liability protection, carrying signs calling for stricter regulation and safer farming practices.

Despite supporting President Donald Trump, they expressed disappointment that his administration is backing Bayer in the case.

For them, the issue is simple: federal approval does not guarantee safety.

“Just because the EPA says something doesn’t make it true,” Linda Martin said.