Doyle is correct.
When the "assault weapons ban" part of the 1994 Crime Bill sunset, it became as though that part of law never even existed on the federal level.
Some states did enact their own versions of that legislation; I don't know the entire list, but as said, GA is not one of them (there's not even all that many of them). If your friend's brother lived in one of those states he'd be limited to those ten round magazines, but that has more to do with the date of manufacture of the magazines than that of the gun itself.
If he wants to, he's more than welcome to purchase full capacity magazines for his pistol. He can keep the 10 rounders as a relic of a bygone age or for range use, or he can sell them to somebody in those unfortunate states. I don't think they'd be of much interest to people in states without capacity limits, at least not without a significant discount over what a full cap mag would run.