Any GameStop employee caught selling an M-rated game to a minor will be summarily fired, according to a recent edict from GameStop's home office. For extra fun, if the employee in question is your standard, underpaid hourly "Game Advisor," his or her manager will get the boot as well.
Although it's never been GameStop's official policy to let the young'uns get their hands on the naughtiness, the company has largely turned a blind eye to the legions of 14-year olds buying various GTAs and Halos. No more, though. In addition to categorically refusing to let a minor buy an M-rated game without a parent or guardian present, all GameStop employees have been told to card anyone "who appears to be under 30." Guess what happens if they don't? They get the Spanish archer, my friends. El-bow.
GameStop: Sell an M-rated Game to a Minor, Enjoy Unemployment [Destructoid]