Under the stated policy, Facebook would allow a user in Texas to list an AR-15 for sale, since the gun is legal there, if it weren't offered for sale in states where it's illegal. But it would delete a similar post from someone in New York. It would, however, remove posts from any state in which the seller says the background check will be skipped, even if such checks aren't required where the seller lives.
In her online petition, Shannon Watts of Moms Demand Action, had written: "There's no way to stop a Facebook or Instagram user from potentially selling a gun to a felon, a domestic abuser or another dangerous person who would otherwise be prohibited from obtaining a gun."
Acknowledging people can't actually sell things to each other through its site, Facebook said many people and organizations use its free tools to promote commercial transactions.
"This is one of many areas where we face a difficult challenge balancing individuals' desire to express themselves on our services and recognizing that this speech may have consequences elsewhere," the company said.
The company said it already has systems in place to remove advertising that's false and deceptive or violates its policies. It already prohibits ads for illegal drugs, tobacco products and prescription drugs.
There's no way to know how many guns are sold via Facebook, because the transactions are actually completed offline, said John Feinblatt, chairman of Mayors Against Illegal Guns. But such sales have occurred. In Kentucky, for example, federal authorities in February charged an Ohio man with illegally selling a 9 mm pistol to a Kentucky teenager, a transaction that investigators say was arranged through Facebook.
Feinblatt noted that Google Plus and Craigslist already prohibit all gun sales. But he said there are "really virtual gun shows" online. His group issued a report in December showing 66,000 active ads on a popular gun sales website called Armslist, up 500 percent from two years earlier.