What irritates me about this issue is that the law-makers that tend to sponsor these bills make it sound like parents have no idea what is contained in the games. It really doesn't take a lot of effort to read a rating label. If it has a big M on it, odds are little Billy may see some things in the game that are not age-appropriate.
Personally, I'm not opposed to enforsing someting similar to how movies are monitored. Make it so that minors aren't allowed to buy rated-M games. That's easy to understand by everyone involved. That way, there aren't all these arbitrary standards that vary from state to state about the types of violence or nudity in the game.
Publishers are always very quick to pounce on the "freedom of expression" argument, since it keeps their wallets fat. They are also quick to point out that M-rated games are aimed at an adult audience, and are not intended for kids. They say that publically, although I know that some publishers clearly expect kids to buy the games, and even base their revenue projections on that fact.
Frankly, as a game developer, I like the rating system. If I work on a game with an M rating, I am aiming at an adult audience and I don't want children to be playing it.
But I think laws like this will be continually shot down as long as the criteria for judging the games is so vague. And frankly, I think the politicians that propose bills like this are perfectly aware of that fact. It allows them to look all concerned for the public welfare, makes them appear to be actively doing something to protect our impressionable children, and when the bill gets shot down (as it inevitably will) they can play the part of the martyred crusader who is valiantly fighting the forces of corruption trying to keep them down. I think if the politicians are sincere, they will attempt to work with the video game industry to formulate a plan to address this issue. And I still haven't seen any true attempt to make that happen.