An anonymous reader quotes a report from NPR: A divided U.S. Supreme Court on Monday heard a dispute over labels on the popular Roundup weed killer , which thousands of people blame for their cancers. How the Supreme Court rules could have implications for tens of thousands of lawsuits against Roundup maker Monsanto, which is now owned by Bayer. The case centers on who decides about warning labels on chemicals: the federal government -- or states or juries. [...] The justices will not be evaluating whether glyphosate causes cancer. Rather, they'll consider who should decide what appears on warning labels and whether states have a role to play after the EPA weighs in. The current U.S. solicitor general backed Monsanto. Sarah Harris, his principal deputy, said the Environmental Protection Agency is in the driver's seat, not anyone in Missouri.…