Some gun owners are using Instagram to resell their firearms, a report by The Daily Beast reveals today, raising questions about how social networks facilitate peer-to-peer gun sales.

Marketplaces like Craigslist often ban the sale of guns, while dedicated gun sites like GunBroker.com require that licensed firearms dealers mediate every transaction. But Instagram has no policy on gun sales, meaning any gun owner can post a photo of an AR-15 assault rifle and wait for the offers to come in. The listings can be found by searching the hashtag #forsale or using the Instagram marketplace Hashbag.

That doesn't mean gun sales on Instagram are illegal, necessarily. It's not illegal to sell guns online, and it's up to the buyer and seller to follow the laws in their respective states. Two gun sellers contacted by The Daily Beast said they were careful to follow applicable laws. "I just Google it," one seller says.

This may be no surprise considering how many people 'grammed their guns on Christmas (and how nice a Glock 9mm looks with a Nashville filter). But the trend isn't limited to Instagram. A quick search by The Verge revealed guns being sold on Facebook and Twitter as well.

everyone I'm selling my glock 22 .40 cal it's only like 7 months old probably been through 1,000 rounds. $400 obo. pic.twitter.com/OyQs5Avs — mikey (@mikeyphelps_4) November 14, 2012

Gun law advocates say these networks are making it too easy to sell guns under the table, underscoring the need for a universal background check — and a 2011 New York City study showed gun owners selling guns online are willing to do so illegally most of the time. Gun rights advocates, however, would say it's nothing new; newspapers have long been criticized for facilitating gun sales through the classifieds.