From Bearing Arms:

Private gun sales are banned from most social media platforms, including Facebook, but a new Wall Street Journal story shows just how difficult it can be to proactively enforce the ban, given the creative ways that users have found to get around the edict.
According to the WSJ, would-be gun sellers are now posting pictures of stickers for sale alongside a gun company logo. Interested buyers are encouraged to contact the seller for more info, and that’s when the talk can turn from stickers to sidearms.