Bayer's shares rose by 11 percent on Friday after the German conglomerate won a significant victory before a U.S. appeals court. The court ruled that Bayer did not violate U.S. state laws by not placing a warning about potential cancer risks on the controversial weed killer Roundup.

The appeals court in Philadelphia unanimously ruled on Thursday that federal regulations take precedence over state law in Pennsylvania. Thus, Bayer was not required to add a cancer warning label to the glyphosate-containing herbicide Roundup.

Bayer, which has been embroiled in expensive and complex legal battles over glyphosate since acquiring the US company Monsanto in 2016, faces compensation claims from thousands of citizens in the US who hold Roundup responsible for their cancer. However, the Leverkusen-based company continues to emphasize that Roundup is safe, citing scientific studies that support this view.

The ruling of the appeals court could pave the way for a review of the legal situation by the Supreme Court of the United States, as it contradicts previous decisions by other federal appellate courts. The court determined that warning labels on pesticides must comply with the requirements of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and not state laws.

The legal dispute reflects the differing views of various authorities on the potentially carcinogenic effects of glyphosate. While the US Environmental Protection Agency (EPA) classifies the substance as safe, the International Agency for Research on Cancer of the WHO classified glyphosate as "probably carcinogenic to humans" in 2015.

In 2020, Bayer reached a $10.9 billion settlement to resolve a wave of Roundup lawsuits and set aside an additional $4.5 billion a year later. Despite several court losses that significantly impacted the stock price, the company launched a lobbying campaign to persuade U.S. states to pass laws that would reduce liability and mitigate legal threats.

Bayer shares were traded at €29.20 on Friday, an increase of 11 percent in the morning trade. Despite the recent price increase, the company's shares have fallen by more than 40 percent in the past 12 months, representing a market valuation of €29 billion.

Bayer expressed its satisfaction with the court ruling and stated that the decision had created a "division among federal appellate courts," making a review by the U.S. Supreme Court necessary. An affirmation of the ruling by the Supreme Court could relieve Bayer of a significant portion of the glyphosate compensation claims.

However, it remains unclear whether the Supreme Court will review the case again, as previous attempts by Bayer to seek a decision from the highest court had failed.