I used to have the facts clearer, but it's become hazy since Fitzgerald's press conference. Fitz's indictment of Libby does a really good job of laying out the timeline of how the leak occured. I think Bush used the fake Niger claim in his Jan. 2003 SOTU speeach. In May, Wilson spoke to the NY Times, & reveals that he had investigated the Niger uranium claim back in 2002 & found out that it was false. The NY Times publishes this info, w/Wilson as an "unnamed ambassador" source. In response to this story, the Bush Administration seems to go into a tizzy & Libby asks the State Dept. & CIA for info about Wilson's background. He discusses this info w/Cheney. In early June, someone at the CIA told the VP's office that Wilson's wife was a CIA agent. The State Dept. memo was written on June 10, 2003, in response to numerous queries by the VP's office about the Wilson trip. This memo reveals Plame's identity, her position in the CIA Counter-Proliferation Unit & her role in sending Wilson on the Niger trip. Then, on June 23, Libby leaks Plame's identity to Judith Miller. On July 12, he leaked her name to Matthew Cooper.
So, the NIE report, as far as I can tell, is totally irrelevant. It never comes up in Fitz's indictment, & doesn't seem to be the source of the information about Plame's identity. The Bush Ad. seemed to first learn about Plame in June 2003, from CIA moles & later from the State Dept. memo. When you read the indictment, it's pretty clear that the VP's office was the motivating force behind finding this info, circulating it, & leaking it to the press. IMO, Cheney is using this NIE thing as a smokescreen to confuse the prosecutors & also the public. It's maybe possible to argue that Bush could declassify something under that stupid unitary executive, but it's a lot harder to make the argument that Cheney can.
http://www.usdoj.gov/usao/iln/osc/documents/libby_indictment_28102005.pdf