Allow Teens to Purchase Mature rated video games without their parents, if they have record of purchasing M games before

I want to allow Teenagers to Purchase Mature rated video games, if they have record at the store that they have purchased other Mature rated video games before with a Parent.
Gamestop, the worlds largest video game provider only lets you buy Mature rated video games with a parent, which is the law. But if you have already purchased M games with a parent earlier, and the computers have record of it, why can't you buy one now.
I think you can make a store account, and eveytime you go to purchase a game they keep record of it and let you buy games without a parent, that you did with a parent.