(MONEY Magazine) – Philadelphia mayor Edward Rendell has been huffing and puffing of late about suing gunmakers. He's looking, of course, at the billions the states are extracting in settlements from the tobacco industry and figures, why not? Guns are worse than smokes.

As public policy, a suit has at least arguable merit. But for investors, it's just scary. If firearms are targeted, alcohol can't be far behind. And what about fatty fast foods? All are legal products that, like tobacco, result in huge public health costs and rely on advertising to create an unduly positive image (a plaintiffs' lawyer might say "fraudulent") and to appeal to youth (though the alcohol industry argues otherwise). Tobacco stocks, FYI, haven't moved in a year.

Gunmakers are next on the hit list for several reasons: They're politically unpopular, school shootings scare the hell out of people, and other mayors, notably Chicago's Richard Daley, are lining up behind Rendell.

Rendell wants to recover $60 million a year in emergency-care and police costs associated with gunfire. In the tobacco litigation, you'll recall, states have claimed that taxpayers should get back Medicaid expenditures for treating smoking-related illnesses.

As their defense, gunmakers fall back on the "guns don't kill, people kill" argument. "Because a product is misused by criminals doesn't mean the manufacturer is liable," says Jack Adkins of the American Shooting Sports Council, an industry lobby group. Michael Ciresi, who represented Minnesota and Blue Cross/Blue Shield of Minnesota in a suit against tobacco companies, agrees. Unlike guns, he says, "cigarettes have no safe level of use. Unless there's evidence of fraud, I don't see a cause for action."

But fraud isn't hard to find, asserts Temple University law professor David Kairys, who has penned a law review article on how to sue the industry. "Gunmakers advertise their weapons as making households safer," he says, "but studies show you're 43 times more likely to shoot a family member than an intruder." Also, Kairys notes, there are more guns made than there are legal buyers; manufacturers know that weapons end up in the wrong hands. That, in fact, is the charge in a pending suit against gunmakers by three Chicago families who had relatives killed by bullets.

The industry has yet to lose in court. But Big Tobacco won consistently too, until states replaced individuals at the plaintiffs' table.

A suit by Rendell would wound gunmakers. But for the lawyers who pursue such a case, the ultimate trophy has to be larger. Total gun manufacturing revenues in the U.S. amount to only $2.5 billion. Anheuser-Busch and McDonald's generate $11 billion each. Now that's big game. Too bad the public isn't allowed to invest in class-action law firms.

--Christopher McDougall