certainly the justification that has been used is COPA.
But I fail to see how getting every single type in query (by everyone) over a week is going to help with Child Porn? Furthermore I don't see how a random sampling of 1 million web pages is going to help with Child Porn either.
Finally I don't see why Google is being required to do the Justice Dept's research. (Guys, if you want it, sit down and start typing.)
[link|http://www.washingtonpost.com/wp-dyn/content/article/2006/01/19/AR2006011903331_2.html|Background]