Facebook Marketplace is being used to sell second-hand firearms, based on a recent report from The Wall Street Journal. Facebook's commerce policy specifically prohibits the sale of weapons, including firearms, BB guns, and even paintball guns, but potential gun sellers are using a basic tactic to avoid being detected.

Instead of simply listing a gun for sale, some Facebook Marketplace sellers are listing gun cases or boxes for sale at a high price and instructing potential buyers to message them for more information. For example, Journal reporters found a North Carolina listing for a gun case priced at $950, though the same case can be found in stores for about $30.

When they messaged the seller, he revealed that he was actually selling an AR-15, the popular semiautomatic rifle that has been used in multiple mass shootings in recent years. The seller shared a picture of the weapon with more than 670 rounds of ammunition and told reporters that he had received more than 30 responses to his post within two hours.

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Potential gun buyers on Facebook Marketplace would likely be able to circumvent a background check before purchasing a firearm. While background checks aren't mandated for private gun sales at the national level, a dozen states have laws requiring universal background checks for all gun sales.

Facebook Marketplace launched in October 2016 and listings for drugs and other illicit products appeared on the platform the same day it launched. Last year Business Insider reported on how easy it is to buy fake jewelry and other counterfeit products on Facebook Marketplace.

Facebook did not immediately respond to Business Insider's request for comment.