Facebook outlined new rules today designed to stop users from illegally selling guns through its social networks. In a blog post, the social network giant said that it will limit posts on Facebook and Instagram discussing the sale of firearms to users over 18, warn people promoting the private sale of weapons to comply with relevant laws, and introduce in-app education on Instagram for those who search for gun promotions or sales. The social network said it would not permit people to post offers to sell regulated items that indicate a willingness to evade or help others evade the law, explaining that private weapon sellers in the US will no longer be able to specify that buyers did not need a background check, and that unlicensed firearms dealers will not be allowed to sell guns across state lines. Any posts reported to Facebook that do reference the private sale of guns will be restricted to viewers who have told the social network they are 18 or older, and the authors of such posts will be warned via a message to comply with relevant laws and regulations. Pages that Facebook classes as primarily used by people to promote the private sale of commonly regulated goods or services will now need to include language that clearly reminds people of the importance of understanding and complying with relevant laws and regulations, and will only be open to users who have indicated they are over 18.