Wow, I could write an essay on why I think this is a bad idea, however, luckily for me, its all already been written in various forms.
Let me first of all state that while I am no constitutional lawyer and my legal knowledge is sorely lacking, I simply cannot see how they would get this through the constitutional courts. As I understand it (and I would really like someone like dominic to comment on this), the rights of children are paramount and we do not recognize the concept of explicit rights, however, that being said, I do not believe that parents lack of ability to regulate their children's behavior on the net results in a violation of the child's right.
Secondly, the technical impracticalities of this are completely bizarre, filtering at a content level at the kinds of speeds we need to get to would be insanely expensive from a hardware and a software point of view, and filtering at an IP level has its own implications which make it completely impractical.
Thirdly, let us consider our current situation in South Africa, where we have huge problems with rape and other crime. A study done at Chapman University demonstrated that access to pornography DECREASED the amount of sex crimes being committed. Since 1993 (When the internet really got going and porn on the net became a lot more wide spread), rape in the United States is down by 72%. When Denmark got rid of their obscenity laws, sex crimes dropped by 50%.
The information in the above paragraph was sourced from a very interesting article I found online that I wish the individuals proposing such a plan would read, it can be found at
http://www.cybercollege.com/sexrsh.htm
This however leads to another point. One of the ways to combat crime is to understand it, and research into a subject requires access to material. As the link above shows, there is active research into pornography on the internet, so by censoring out the internet, you effectively not only censor the population, but you shut down the ability to research the subject and find better ways of dealing with it.
Bottom line, I find this entire thing completely ludicrous
I have to state at this point that the views expressed above are entirely my own and not necessarily representative of TENET or any other organization which I may be associated with.