This isn't any different than walmart already currently is...
All it is enforcing the whole point of ESRB. And as a responsible parent you can buy a game for your kid.
I don't care much either way as it doesn't affect me in the slightest, and if I have a kid, I wouldn't let him play GTA when he's 10 anyways, but they should enforce the ESRB ratings, or abolish it all together as it's a waste otherwise imo.