How would they apply this rule to websites hosted overseas? Or in other states?
I would say they are expecting other states to do similar laws and at some point offer reciprocation. They know the technology is coming where they will be able to enforce such a law so they are just getting a head start. Pretty soon people are going to be using the internet mostly with smart phones and tablets...with chip IDs and GPS tags and all sorts of ways to track down the user. Photos already have ID markers embedded in them so that you can tell what smart phone took the pic and where and when. They will be doing the same with text too, I suspect.