The Supreme Court seems divided over whether to block thousands of lawsuits alleging the maker of the weedkiller Roundup failed to warn people it could cause cancer. The case came before the justices Monday after a tidal wave of litigation that included some multibillion-dollar verdicts against the global agrochemical manufacturer Bayer, which owns Roundup maker Monsanto. Several justices seemed sympathetic to the company’s argument that it can’t be sued under state law because federal regulators have found Roundup likely doesn’t cause cancer. Others, though, grilled attorneys about whether that wrongly stops states from responding to new research pointing to possible links.