Justices at the U.S. Supreme Court appeared split on Monday over whether a federal law that regulates the sale and marketing of pesticides preempts state-level lawsuits against manufacturers. The case centers on whether the federal government — or states — should decide what warning labels should be put on herbicides. Its main plaintiff is a Missouri man who sued Monsanto and its parent company Bayer in 2019 over its popular weed killer, glyphosate, marketed as “Roundup.” He alleged two decades of exposure to the chemical caused him to develop blood cancer. A jury found that Bayer had failed to warn him of the risks associated with Roundup, and awarded him $1.25 million in damages. The Trump administration, which has called Roundup safe, is siding with Bayer in its challenge at the Supreme Court. If successful, thousands of lawsuits alleging cancers caused by Roundup could be thrown out.