If you own the rights to your own data you can prevent that data from being made public (or used in other ways). A nation state can very well require that social media sites honor this if they want to operate in that country. Search engines can also be forced to delete data etc.

Granted I doubt it's practically enforceable in all cases but it's at least theoretically possible. It would be cool if such a button could be detected and people wearing it would get blurred by the photo-software of cell phones automatically.