Currency blocking is fairly straightforward though. A banned set of images, perhaps some blocked color values or whatnot. But there's a huge space of possible

Currency blocking is fairly straightforward though. A banned set of images, perhaps some blocked color values or whatnot. But there's a huge space of possible gun designs. Don't we need a large advance in technology to be able to determine something is a gun? Especially if we don't accept a lot of false positives?