From truthout.org :
White House Subpoenas, and a Constitutional Showdown
Matt Renner reports: "Subpoenas issued Wednesday by Congress for testimony from former White House officials could lead to a constitutional crisis over the right of executive privilege. Experts in constitutional law believe that the Bush administration will not comply with the Congressional subpoenas and will force a showdown.
If individuals do not comply with the subpoenas, a vote can be taken to hold them in contempt of Congress. The issue would then be sent to the Washington, DC Circuit Court, where the US attorney for the District of Colombia could prosecute the case before a grand jury."