Yeah, but defense in depth requires that each layer make the security strictly better, or, at least, not introduce a huge vulnerability. If a non-cop picks up

Yeah, but defense in depth requires that each layer make the security strictly better, or, at least, not introduce a huge vulnerability. If a non-cop picks up a tagged gun, that seems like it makes them more easily confused as as a good guy, and thus a lot more dangerous. And if you were already able to reliably distinguish plainclothes-cop from plainclothes, then what does the tagged gun add? What am I missing here?