The White House/Pentagon/Downing Street Conspiracy

Digby has an interesting, and plausible, take on what the special prosecutor may now be looking at. Bottom line: a broader conspiracy to intentionally lie to the American people in order to get them to support declaring war on Iraq.

My question for the legal types out there: What might possibly be illegal about this? Lying to the public is a bad thing, but is it illegal?

I do know that the State Department is forbidden BY LAW to propagandize to the American people - if they were involved in this effort to influence the American people, whether with the truth or a lie, then PER SE it's a crime.

But what about the other agencies and the White House? Where's the crime here?

I'm not saying there isn't one, I'd just like to know what it is.