I meant to post this, too. Slate's Dahlia Lithwick is one of the few to actually ask what exactly Zacarias Moussaoui is being tried for:

Scrutinizing the indictment, three possibilities emerge: the government is not presenting crucial evidence tying Mr. Moussaoui to the Sept. 11 attacks; the government has no evidence tying Mr. Moussaoui to the Sept. 11 attacks; or federal conspiracy law is so infinitely elastic that Mr. Moussaoui could receive the death penalty for simply buying knives, learning to fly and training in Qaeda camps.
http://www.nytimes.com/2002/08/02/opinion/02LITH.html

(I was, though, bugged by the grammatical error is the first sentence, which suggests that the possibilities themselves have done the scrutinizing. Grrr.)