Facebook has banned sales of private firearms on the social networking site and on the photo-sharing app Instagram, a company spokesperson told NBC News Friday.

"Over the last two years, more and more people have been using Facebook to discover products and to buy and sell things to one another. We are continuing to develop, test, and launch new products to make this experience even better for people and are updating our regulated goods policies to reflect this evolution,” said Monika Bickert, Facebook’s head of product policy.

A Facebook spokesperson said that the policy only applies to "peer-to-peer" sales of guns, but not advertisements for guns that are posted about on Facebook by licensed retailers. " Licensed firearm retailers will still be able to post about their goods and services on Facebook while completing sales transactions off Facebook," the spokesperson said.

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Facebook had already banned sales of marijuana, pharmaceuticals, and illegal drugs on the site. Those things, along with illegal guns, are also not allowed to be advertised on the site.

The spokesperson said that the company has systems in place to review and remove content that violates the new and previous policies.

The advocacy groups Everytown for Gun Safety and Moms Demand Action for Gun Sense said they had been discussing the possible policy change with Facebook for two years.

"We're gratified that our continuous conversation with Facebook over the course of the last two years has culminated in the company prohibiting all unlicensed gun sales arranged on its platforms," said John Feinblatt, the president of Everytown for Gun Safety. "Our undercover investigations have shown that criminals are active in the online market for guns, where unlicensed sellers can offer guns with no federal background check required.”