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Facebook is going to censor posts advertising gun sales without background checks. 

Facebook says it won't permit people to post offers to sell regulated items and indicate they're willing to help people evade the law. 

The social media site said it consulted with gun control groups like Mayors Against Illegal Guns to come up with the policy change. 

The National Rifle Association on Wednesday blasted Mayors Against Illegal Guns for trying to inhibit free expression on Facebook.  (Metro Networks Inc.)