The operative law is 18 USC 701. However, frankly, it's a bit tenuous if he's defaced it first, and it's not even clear that photocopying something like a CAC card which isn't going to be fooled like perhaps makign color copies of your old-style reserve id card or whatever is. Again, I'm not sure why he cares if the unit doesn't.
I'm a bit unclear as to what you're asking, FaheyUSMC (and by the way, thank you for your service).
Are you asking if YOU can get in trouble for sharing the picture of his CAC that he provided you, or are you asking if HE can get in trouble with showing you his CAC?