Dude, this has been going on for a while. R rated movies, M rated games, it's nothing new....I don't know what you're complaining about, it's just the law.
Just be glad our rating system isn't as harsh as some countries. Germany wouldn't even rate GoW, so they can't buy it there at ALL (so I hear).
Alot of stores are stepping up this policy. This law has been in effect for a while, but many stores haven't been enforcing it that well in the past. Many store clerks will even let some teenagers off without checking for an ID (Many make the assumption that they look over 17).