Lots of info here, from someone who just might know.
http://www.smirkingchimp.com/thread/4675The Arsenal of Tools Congressional Democrats Can Use To Force the Bush Administration To Cooperate
by John W. Dean
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Congressional Subpoenas and Contempt Powers
There is nothing subtle about the use of subpoenas, which can be used against Executive Branch officials or private individuals. If the witness claims the Fifth Amendment right to remain silent because of self-incrimination, the Congress can grant the witness either "use" immunity, precluding the use of the witness's testimony or its fruits in a criminal prosecution, or full immunity, which precludes criminal prosecution for stated charges on any evidence, no matter how it is discovered.
The difference between use immunity and full immunity, however, is often immaterial. In high profile cases - such as that of Oliver North, who provided immunized testimony during Iran Contra - it is virtually impossible to prosecute the witness, for the testimony may have influenced potential jurors. Prosecutors, and the Congress, generally understand that the Congress's right to information can preclude the government prosecuting in many situations - though sometimes they do try to indict anyway.
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Unique House Tools: Resolutions of Inquiry and the "Seven Member Rule"
There are a few tools only the House can use. For example, a House resolution of inquiry makes a direct "request" of a president, or a "demand" of other Executive Branch officials, to produce information. It is a tool that allows any member of the House to seek information.
The resolution is privileged, and if it is not reported back from the committee with jurisdiction within fourteen days (with the report stating their approval or disapproval), the member introducing it can file a motion to discharge the committee, and this is a privilege motion -- which means it is always in order to file it. Typically, the House debates a resolution of inquiry for one hour, and then votes it up or down.
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The Executive Privilege Shield
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Members of Congress thus face a serious problem when a president exerts executive privilege, demonstrating that he (or she) is willing to spend the necessary political capital, and suffer the inevitable parallels to Nixon. In this situation, there is really nothing the Congress can do - short of impeaching the president on the theory that his improperly withholding information amounts to a high crime or misdemeanor, which itself could, of course, be a reach.
Suppose the 110th Congress does find itself being stonewalled by Bush and Cheney's claims of executive privilege. Does it then have no recourse?
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