I'm sorry, but I honestly can't get my head around how this is as bad as everyone is saying. I live in the UK and there are legal age restrictions on buying games, like there are on buying films/alcohol/gambling/cigarettes/pornography and even going to the cinema. It doesn't stop us getting any of the gory titles (I don't think), all it means is that you have to be 18 to buy some of them (not that it stops kids getting them).
Reading through Alexander Macris article, a lot of it seems based on assumption. Why would distributers not sell in California? It's still money they'd be making. Why would Wal Mart etc need to spend loads of money on training? What training do you need to ID someone? I was a barman for 5 years, I never had any special training in order to ask someone for ID. I disagree with censoring games, but do we even know that's what they are going to do? Again, if it's a "possible", then I'd say it's pretty unlikely, as it's the only part of this which is unconstitutional (from what I beleieve)
I don't agree that this state law is necessary, but it primarily seems to be a problem with you guys because of your constitution, which makes it seem like you are crying over spilt milk (from over here). Or have I missed a major point?
At the end of the day, you don't want games to be treated differently to books or films, but they ARE different. They are interactive media, and as Macris pointed out, everything is becoming more and more interactive. These things need to be legislated, otherwise it is a judicial nightmare, like the internet can be. Sometimes you need to take a step back before you can make a leap forward, and I'm not yet convinced this is even a step back.
(Edited)
Again, if I've missed a major point, please let me know