There may not be any laws clamping down here in CA, but I can assure you stores have their own policies restricting minors from buying games. It's a localized sort of thing in terms of laws. Restriction is done more according to individual communities as opposed to a statewide law. CA might as well be 4 or 5 different mini-countries while we're at it.
It isn't unheard of that schools in a given town will also complain about games, mini devices, personal electronics, laser pointers, and the like, to have their local government create ordinances that the stores must follow or they get fined. Sort of like the cliquish, spiteful, home owner associations with vindictive chips on their shoulders.
I digress, schools have a great influence on what laws are passed, though hardly absolute power. The power owes more to the fact that this localized scheme of laws speaks more specifically to the tastes of residents of a given area.
For example: In Sacramento where there is more crime related to violence, esp. western Sac, laws may be tightened more for violent games than nearby Napa Valley or Placerville. Or some companies who have faced lawsuits elsewhere may take the initiative within its stores in order to prevent further lawsuits. Radio Shack won't sell laser pointers to anyone under 19.
"I wasn't counting cards, I was cheating."
"Ugh. you give me hives."
"It's Tee-revor time!!!"