Mack,
What is at issue is whether or not the 2 states can agree on recognizing each others permits. SC has always been notorious for wanting to do things their own way and refuses to recognize GA's (and AL and MS for that matter) permit because they are not happy with the way the law in those states is written. Since SC refuses to recognize their permits, none of the states I mentioned recognizes the validity of an SC permit either.
I live in AL and can empathize with you. The state law here leaves it up to the discretion of the County Sheriff as to what the exact requirements and fees are for a Pistol Permit. That means there's about 40+ different sets of requirements and which county you live in decides what you need to do to get a permit. A LOT of states don't like this set up and refuse to recognize AL permits because it's not written in state legal code what the requirements are. In return, AL won't recognize their permits either.
It's actually kind of amusing because the Brady Bunch see a vague 'May Issue' law on the state books and give AL a good grade because of it when the reality is getting a permit in all the counties of AL I've ever heard of is simple (I filled out the application and waited a week to hear back on the background check- no fingerprints or any of that other stuff), reasonably priced (I pay $20 a year) and is treated as 'Shall Issue' in all but name.