From my reading of NC 14-409.10. "Purchase of rifles and shotguns out of State" I would guess that if the person has a valid CCW (which satisfies the background check requirement) you should be good. If they don't, you need an FFL involved to get a background check. I would have him come to SC so he is purchasing "out of state" as the law (and SC's equivalent) cover purchases out of state, but say nothing about an out of state seller.
I'm not a lawyer, that is a lay persons interpretation and not legal advice. Honestly, I would avoid the risk and just involve an FFL as it is cheap compared to legal fees (even if you win).