The film follows the initiation of an office drudge Wesley Gibson (played by James McAvoy) into a mythical group of super-powered assassins. The ad for the DVD release shows McAvoy and co-star Jolie wielding pistols, a shotgun, and generally spraying scene after scene with bullets.
The authority said the ad — which juxtaposes images of gun violence with Jolie showing off her bare back — "could be seen to condone violence by glorifying or glamorizing the use of guns."
It was unclear what practical effect, if any, the ruling would have. The "Wanted" DVD was released in Britain nearly six months ago.
The advertising authority has no power to enforce its writ, but it can refer advertisers to Britain's Office of Fair Trading for legal action.
Universal did not immediately return an e-mail Wednesday seeking reaction to the authority's ruling.
The ruling underlined Britain's sensitivity to gun crime.
There were 59 firearm-related homicides in England and Wales in 2006-2007, compared to the more than 10,000 gun-related killings reported by the FBI in the United States in 2007.
But public concern was heightened in Britain after the shooting death of an 11-year-old boy in 2007. The murder drew national attention and prompted much soul-searching over whether the country's already strict gun control laws were tough enough.