Fellner's lawsuit has the potential to open the door to thousands of personal injury lawsuits against tuna companies over the mercury issue, and if successful, it could also help the state of California prevail in its efforts to put warning labels on tuna cans advising about the mercury risks, a move that could cost the tuna industry millions in lost sales. So Chicken of the Sea appealed to the high court, which this month requested a response from Fellner, a sign that the court may be seriously considering the preemption issue raised by the tuna company.

Preemption is a hot topic at the court these days. It's already decided a number of preemption cases in the past year, most recently in Altria v. Good. In that case, the court found that lawsuits against the cigarette company for deceiving customers into thinking that "light" cigarettes were healthier for them were not preempted by federal regulations. The case represented a huge win for those who see preemption as a threat to many state consumer protection, health and safety laws. But the court has also ruled the other way. In February last year, in Riegel v. Medtronic, the court ruled that a 1976 law did preempt lawsuits filed against the makers of medical devices who'd undergone extensive safety testing required by the FDA, even when those devices were defective and killed people. That decision prompted a Minnesota judge recently to throw out more than a thousand lawsuits filed by people who'd been injured by faulty pacemakers. (Congress is now considering legislation to overturn that decision.)

Still, Fellner has a decent chance of prevailing, one way or another. Even if she loses, she'll succeed in raising public awareness about mercury in tuna simply from the publicity likely to surround the case if it reaches the Supreme Court. And that can't be good for the tuna companies, which would prefer that Americans see their canned tuna products as a recipe for good health, not a delivery system for dangerous neurotoxins.