(Reuters) – Bayer is on track for its best day on the stock market since 2008 as the pharmaceutical company won a U.S. court victory in its battle over its Roundup weedkiller.

A federal appeals court in Philadelphia said federal law shields the German group from a lawsuit brought by Pennsylvania landscaper David Schaffner, who claimed that Bayer’s Monsanto subsidiary failed to put a cancer warning on the Roundup label.

David Schaffner was diagnosed in 2006 with a form of cancer called non-Hodgkin’s lymphoma, a common condition among Roundup plaintiffs. He and his wife Theresa filed a lawsuit against Bayer in 2019.

The federal appeals court in Philadelphia said the Federal Insecticide, Fungicide, and Rodenticide Act required uniformity in pesticide labels nationwide and prevented Pennsylvania from adding a cancer warning.

Bayer said the decision conflicted with rulings by federal appeals courts in San Francisco and Atlanta in similar cases.

It is therefore possible that the US Supreme Court will step in to decide the dispute, which could reduce Bayer’s liability.

Chip Becker, the Schaffners’ attorney, said he was disappointed with the decision and said federal law should not prevail over his clients’ failure to warn claim.

Bayer maintains that Roundup and its active ingredient, glyphosate, are safe and said it “continues to fully support” the brand.

Bayer, which has been facing numerous litigation over Roundup, has seen its stock price fall more than 73% since its $63 billion acquisition of Monsanto in June 2018.

The German group settled much of the Roundup litigation for $10.9 billion in 2020, but still faces about 58,000 claims. Another 114,000 have been settled or ruled inadmissible.

Although Bayer had won 14 of 23 Roundup-related lawsuits through July 23, one victory was overturned on appeal and the losses earned it billions of dollars in damages.

The Schaffners reached a settlement with Bayer in September 2022, on the condition that Bayer fail to convince the courts that federal law prevented Pennsylvania from requiring a cancer warning.

On the Frankfurt Stock Exchange, at midday, Bayer shares were up almost 12% to 29.43 euros.

(Jonathan Stempel in New York; with Brendan Pierson and Ludwig Burger; Elena Smirnova; edited by Jean-Stéphane Brosse)

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