The Justice Department is denying a subpoena from House Judiciary chair John Conyers for documents relating to the prosecution of former Alabama governor Don Siegelman.

Conyers is investigating whether the 2006 prosecution on corruption charges of Siegelman, a Democrat, was politically motivated.

In a letter sent Friday to Conyers, Principal Deputy Assistant Attorney General Keith Nelson writes that DOJ won't produce the documents in question, consistent with a department policy of not providing internal prosecution materials to Congress. Nelson makes the contorted argument that even though such documents in fact have been given to Congress in the past, that would not affect the decision on the Siegelman documents, because of supposed uncertainty about the facts of the other cases:

We do not believe that a possible departure from those policies in any given matter, the details of which may not be known or knowable at this point, requires us to set them aside in any other matter.

In response, a Judiciary Committee aide told TPMmuckraker:

Not sure when DOJ starting getting Donald Rumsfeld to write their letters, but I don't think the Committee's subpoena can be put off by some Justice Department Uncertainty Principle that refuses to answer Congressional oversight based on the unknowable nature of facts. In the end, this wrangling over oversight precedent misses the important point here - the Department's reputation is at a low ebb, and they should be working to clear away the clouds over the Siegelman case, not hunkering down and hoping they'll blow over.

At a 2002 press conference, Rumseld famously told reporters, in regard to whether Saddam Hussein had tried to pass weapons of mass destruction to terrorists:

[A]s we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns -- the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones.

Last week, we reported on new documents that have surfaced in the Siegelman case, showing, among other things, that the U.S. Attorney on the case -- who had recused herself because her husband is a top GOP operative who had run the gubernatorial campaign of Siegelman's GOP opponent -- continued to advise prosecutors.

In an interview with TPMmuckraker, Siegelman lamented what he called "outrageous criminal conduct" on the part of the US Attorney's office and main DOJ.