I dont think its possible to enforce rules like this.
But if we are talking about IF it was possible.
I would still disagree to video games age restriction by the law.

Because every parent wants their children to be a certain way.
We shouldn't try to make everyone similar.
If I had a child I personally wouldnt mind him playing any video game as long as he doesnt end up scared of his own shadow. And with 5 minutes of research I could find out if the game he is playing has that impact. And easily convince or force him to stop playing it.
And I wouldnt mind him seeing naked women in video games. I know this doesnt cause addiction. I've been playing games like gta sa and god of war and WWE which allows u to dress a half naked woman, since I was like 8, And I'm not addicted to pornography.
But some parents on the other hand would probably be real strict and not want their child to play any other games than super mario.
And regardless of law, a parent can choose what their child has access to anyways. So the whole idea of restriction by law is not a great one.