Failure to comply with Congressional subpoena isn't contempt of Congress subject to the procedures already detailed in a previous post?

Congress can subpoena witnesses, or force them to testify under oath, before its committees. This authority comes from the Constitution's grant to Congress of “all legislative powers” (Article 1, Section 1). Witnesses are subpoenaed to provide information that will assist committees in preparing legislation. In the case of Mc-Grain v. Daugherty (1927), the Supreme Court recognized that Congress could subpoena even private citizens to testify. The Court noted that since not everyone would volunteer needed information, “some means of compulsion are essential to obtain what is needed.” Witnesses who refuse to respond to a congressional subpoena, or refuse to give information (unless they invoke their 5th Amendment protection against self-incrimination) may be found in contempt of Congress and sent to prison.

The most famous use of the congressional subpoena occurred in 1973, when the Senate Select Committee on Presidential Campaign Activities (popularly known as the Watergate Committee) subpoenaed the tape recordings that President Richard M. Nixon had secretly made of White House conversations. This was the first time that Congress had ever subpoenaed a President. Nixon tried to withhold the tapes, claiming executive privilege (the right of the President not to release internal documents of the administration to the Congress). The courts ruled that the President could not use executive privilege as blanket protection, but the White House then released only a heavily edited version of the tapes. In June 1974, in United States v. Nixon, the Supreme Court ruled that executive privilege was a limited power and that the President must turn over all of the requested tapes to a special prosecutor investigating the Watergate incident. The opening of these tapes led Congress to begin impeachment proceedings against the President, causing Nixon to resign.


Read more: http://www.answers.com/topic/subpoena-power-of-congress#ixzz1YY0Rg9wQ