One recurring argument that Bayer Corp. has made in the swarm of cases claiming that Roundup causes cancer is that federal law concerning the product’s warning label should preempt state law claims that the company failed to warn consumers.

Those arguments have so far been unsuccessful in persuading state and federal trial courts in California, home of the lion’s share of the trial court action in Roundup cases thus far. The company currently has appeals pending on the preemption issue before the Ninth Circuit and California Court of Appeal.