This whole thing reminds me of a "Big Picture" episode.
I don't understand why there needs to be a law for everything and especially to save people from their own stupidity and absolve them of their responsibility.
Parents should be PARENTING. There is now way around it. The law cannot do it for them.
If someone is too indifferent to care, learn or even monitor the ESRB, PEGI or whatever is valid for his territory, if someone doesn't invest the time to know what their non-adult children are playing, then I don't see how the law, or retailers can do it for him/her.
I agree that the ESRB / PEGI ratings are a bit over the top, but still, they are a valid way to choose what your 7 or 8 year old child should be exposed to. Giving Manhunt or GTAIV to a 10 year old might not be the brightest idea. Generally, giving a M or 18+ game to a kid under 14-15 seems to be exposing them to more than they can handle. Same stands for movies. Same stands for books (don't hand H.P. Lovecraft or Clive Barker to a 12 year old). I know they can easily find sex and violence in the internet, but that doesn't mean that they want to or will actively pursue to.
I think that such legal regulation is stupid and thinks that all people are unfit for parenthood and plain dumb.