How would banning these be enforceable though? They are only going to get more discreet, they will eventually appear completely indistinguishable from regular glasses.

There are certain ways to detect cameras, such as monitoring for infrared, but that would not work for all camera tech and could be hard to triangulate to exact people in crowded areas. There are also ways to detect electronic devices on a person but doing so could quickly become just as invasive in other ways.