By Carrie Johnson | NPR

The Supreme Court agreed to shield Monsanto from liability over its popular weed killer Roundup, dealing a victory to the company's new owner as it struggles to resolve thousands of costly lawsuits from people who claim the key ingredient caused their cancers.

The central issue in the case, filed by Missouri resident John Durnell, is who decides what should appear on a pesticide or insecticide label—and whether a federal law overrides state claims.

The Justice wrote in a 7-2 opinion written by Justice Brett Kavanaugh that the Federal Insecticide, Fungicide, and Rodenticide Act, or FIFRA expressly preempts state law and Monsanto's failure to warn consumers about the dangers of glyphosate.

Justice Ketanji Brown Jackson filed a dissenting opinion, in which Justice Neil Gorsuch joined.

Monsanto, now owned by Bayer, argued a federal law gives the power to set the label to the U.S. Environmental Protection Agency, not to the states. The company's lawyer, former Solicitor General Paul Clement, told the Supreme Court there's a need for a single, uniform standard and that the Federal Insecticide, Fungicide, and Rodenticide Act puts the EPA in charge.

"You shouldn't let a single Missouri jury second-guess that judgment," Clement said during oral argument in April.

The current U.S. Solicitor General, John Sauer, sided with Monsanto — as did the majority of the Supreme Court justices.

"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 in the court's majority opinion.

Experts said a ruling for the company could significantly narrow its liability in tens of thousands of cases moving slowly through the courts.

But a lawyer for Durnell argued there's room for state juries to weigh in on Monsanto's alleged failure to warn consumers of the dangers of glyphosate, the central chemical in Roundup.

Ashley Keller told the justices that Congress has been debating a golden shield for the company as part of the farm bill. But until Congress acts, Keller said, state juries could and should still be able to evaluate such cases.

Jackson, in her dissent, agreed, and said the majority misunderstood FIFRA's requirements, saying adding a cancer warning doesn't conflict with the law.

"In accepting Monsanto's argument and holding that Durnell's failure-to-warn claim is preempted, the Court misunderstands FIFRA's requirements, misinterprets the scope of FIFRA's preemption, and ultimately leaves Durnell without a remedy for the significant harms he has suffered," she wrote.

Scores of protesters appeared in front of the Supreme Court in late April to support people who say they were harmed by the weed killer and other chemicals, in allegiance with the Make America Healthy Again movement.

President Trump has signed an executive order to boost domestic production of glyphosate, which has contributed to a rupture between the White House and some MAHA supporters.

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