Laws protecting consumers from false advertising of products are enforced pretty vigorously. For example, the Federal Trade Commission (FTC) took action in 2002 to protect the public from the self-proclaimed psychic "Miss Cleo," whom the FTC said promised free readings over the phone and then socked her gullible clients with enormous telephone charges. The FTC even forced a toy company a while back to stop running ads showing its "Bouncin' Kid Ballerina Kid" doll standing alone and twirling gracefully without human assistance, which the FTC said was video hokum.
But there's no such truth-in-advertising law governing federal candidates. They can legally lie about almost anything they want. In fact, the Federal Comunications Act even requires broadcasters who run candidate ads to show them uncensored, even if the broadcasters believe their content to be offensive or false.
And of course, if the ad is true, case closed.
On the other hand, this is an ad run by an independent group, not Kerry's opponent. I wonder if that matters?
As another pointed out, the purpose here is not to win, but to delay. After Sept. 3rd, the ads can not air regardless of the outcome of any legal action.