Here is a relatively recent North Carolina law on license plates. My apologies if this has been posted before. I searched thoroughly and found nothing on this.
The nutshell version of the law is, no "information" at all may be covered by your license plate frame.
I am not sure how often police enforce this law; it is probably just selectively enforced like our tint laws or when a LEO gets angry or bored.
Here is the NCDOT release:
And here is an article on the new law: