"They said, '100 percent beef.' I thought that meant it was good for you," Barber claimed after filing the lawsuit in July 2002. "Those people in the advertisements don't really tell you what's in the food. It's all fat, fat, and more fat. Now I'm obese."

Hirsch eventually dumped Barber in favor of two hefty New York teenagers who claimed to have eaten at McDonald's on most days of the week for years. That lawsuit, which Hirsch intended as a class action, was dismissed twice, the second time with prejudice, for failing to adequately state a claim.

Yet as Banzhaf and others noted, U.S. District Judge Robert Sweet left the door open to arguments alleging that some aspects of fast food fare are not widely recognized. A plaintiff might make headway by arguing that fast food is addictive, for example, or that certain highly processed dishes are not what they seem, containing more fat, calories, or cholesterol than the average consumer expects.

Victor Schwartz, a leading expert on tort law who has been advising the National Restaurant Association, says these lawsuits still face formidable obstacles. He thinks a greater danger to the industry is that at some point state attorneys general will start filing lawsuits demanding compensation for Medicaid expenses, as they did with tobacco.

And herein lies the strongest rationale for congressional intervention, even if it means telling state courts which lawsuits they may hear -- a prospect that should make federalists uncomfortable. The agreement that settled the state tobacco lawsuits in effect imposed a nationwide tax and nationwide regulations, including advertising restrictions that would have been unconstitutional if imposed by statute, without approval from Congress or any state legislature.

A similar arrangement with food companies (or gun manufacturers, the concern of the other NRA) likewise would usurp the authority of state and federal legislators. Although condemned as contrary to the balance of powers created by the Constitution, legislation aimed at preventing such a scenario may be necessary to preserve it.