McCain-Feingold does not ban ads inside the 60-day period that discuss important issues in an election without identifying a candidate.

The M.T.A. has tried in the past to ban ads that criticized it.

Banning advertisements by political parties makes sense; banning ads by independent issue-oriented groups does not.

Even so, the report found that game companies routinely violated that prohibition, and recommended further tightening, perhaps by banning ads on sites with obvious youth appeal.

Broadcasters have banned the promotion of 'inappropriate products' during Benedict's visit, as well as ads carrying any whiff of sexual innuendo.

In the mid-1960s some newspapers began banning ads for the films.

It also ruled in June 2007 that banning ads mentioning candidates by name within 60 days of the general election was unconstitutional.

It would ban such ads close to an election - within a period yet to be determined --except in an emergency, Mr. Vallone said.

If we banned political ads, like cigarette commercials, as dangerous to public health, that would only give incumbents a corrupting hold on power.

Still, Dr. Galson said that banning ads for one drug made little sense when similar pain pills have similar risks.