Video Game Laws

I know that I've posted three times today, which is kind of a lot, but I really want to write this stuff down instead of waiting for a later date.

When I was at Wal*Mart buying my copy of GUN, probably sometime in December, I went up to the counter with my mom because I am under 17. I was going to pay for the game, and my mom was going to give permission for me to buy it. The lady wouldn't allow it. She said that store policy was no sales of M-rated games to minors at all. I tried to give my money to my mom so that she could buy it, and the lady said no again. I was still paying for it. My mom said that she would pay for it herself, and the lady said that she needed to hold the game so that someone could take it back to the shelf.
I went all the way back to the back of the store and picked up another copy of the game, gave it to my mom, went in a different isle and my mom bought the game for me. I paid her back, but still, both of us were kind of angry about it.

To clarify: the only law about the sale of M-rated video games to minors is that they must have the permission of an accompanying parent or adult. Whether or not it is legal or whatever for stores to have their own policies like that is something that I do not know. What I do know, is that it is annoying.