SAN FRANCISCO--A San Francisco transit agency spokesman says the city is investigating whether pro-gun ads, which an advocacy group recently purchased, should have been posted in transit stations this week.
The city's policy on such ads is strict but clear: It says that "no advertisement" shall "promote the use of firearms."
"We're reviewing the matter as we speak," Paul Rose, a spokesman for the San Francisco Metro Transit Authority, told CBSNews.com. "I don't have a timeline. At this point they'll remain up."
San Francisco, of course, takes a famously dim view of gun rights. A ballot initiative to ban handguns easily passed a few years ago, before being overturned by the courts, and some residents in one neighborhood are trying to drive the one remaining gun shop out of town.
Which is why the SFMTA's policy should come as no surprise. It was used as recently as last month to force a poster for the Will Ferrell-Mark Wahlberg film "" to be redrawn. No longer do the two stars brandish handguns; instead, Ferrell is holding pepper spray.
"Well, the San Francisco Municipal Transportation Agency does have an advertising policy that states ads should not appear to promote the use of firearms or advocate any violent action," Rose told the SF Weekly newspaper at the time.
The new ads -- which the Second Amendment Foundation purchased and which appeared this week -- appear to violate SFMTA's policy. The ads show (PDF) an Asian-American woman peeking through a curtain armed with a pump shotgun. The accompanying text: "A violent criminal is breaking through your front door. Can you afford to be unarmed?"
Rose said in a telephone interview that SFMTA didn't know about the ads in advance (the agency outsources advertising to Clear Channel Outdoor). "The vendor's responsible for reviewing the ads' compliance with our advertising policy," he said.
A Democratic source close to the San Francisco Board of Supervisors said Thursday that: "I'd hope that they'd look into that and not let these things slip through the cracks."
The potential legal problem for the city is not the Second Amendment, but the First Amendment. It generally prohibits government agencies, including city governments, from approving or rejecting otherwise legal advertisements based on their political message.
(In a case brought by the Second Amendment Foundation, the U.S. Supreme Court ruled in June that the Second Amendment protects Americans' rights to possess handguns, even if local governments such as Chicago would prefer otherwise.)
Second Amendment Foundation founder Alan Gottlieb says that if San Francisco takes down the advertisements, which also promote his group's gun rights policy conference in a nearby suburb, he'll see them in court: "All I can do is pray that all the publicity will make them want to decide to take down the ads -- so we can sue!
Declan McCullagh is a correspondent for CBS Interactive's CNET News and a contributor to CBSNews.com. You can e-mail him or follow him on Twitter as declanm. Declan previously was a reporter for Time and the Washington bureau chief for Wired.