ASSOCIATED PRESS: Former White House adviser Karl Rove defied a congressional subpoena to testify Thursday about allegations of political pressure at the Justice Department, including whether he tried to influence the prosecution of a former Democratic governor of Alabama. Rep. Linda Sanchez, chairman of the House subcommittee that called Rove, ruled with backing from fellow Democrats on the panel that Rove’s claim of immunity was invalid – perhaps the first step toward holding him in contempt for refusing to cooperate.
Lawmakers subpoenaed Rove in May in an effort to force him to talk about whether he was involved in prosecutors’ decisions to pursue cases against Democratic politicians or in the firing of federal prosecutors two years ago.He had been scheduled to appear at a House Judiciary subcommittee hearing Thursday morning. A placard with his name sat in front of an empty chair at the witness table, with a handful of protesters sitting behind it calling for Rove to be arrested. MORE
WIKIPEDIA: Following the refusal of a witness to produce documents or to testify, the Committee is entitled to report a resolution of contempt to its parent chamber. A Committee may also cite a person for contempt but not immediately report the resolution to the floor. In the case of subcommittees, they report the resolution of contempt to the full Committee, which then has the option of rejecting it, accepting it but not reporting it to the floor, or accepting it and reporting it to the floor of the chamber for action. On the floor of the House or the Senate, the reported resolution is considered privileged and, if the resolution of contempt is passed, the chamber has several options to enforce its mandate, including Inherent Contempt. Under this process, the procedure for holding a person in contempt involves only the chamber concerned. Following a contempt 
citation, the person cited is arrested by the Sergeant-at-Arms for the House or Senate, brought to the floor of the chamber, held to answer charges by the presiding officer, and then subjected to punishment as the chamber may dictate (usually imprisonment for punishment reasons, imprisonment for coercive effect, or release from the contempt citation.)
Concerned with the time-consuming nature of a contempt proceeding and the inability to extend punishment further than the session of the Congress concerned (under Supreme Court rulings), Congress created a statutory process in 1857. While Congress retains its “inherent contempt” authority and may exercise it at any time, this inherent contempt process was last used by the Senate in 1934, in a Senate investigation of airlines and the U.S. Postmaster. After a one-week trial on the Senate floor (presided over by the Vice-President of the United States, acting as Senate President), William P. MacCracken, a lawyer and former Assistant Secretary of Commerce for Aeronautics who had allowed clients to rip up subpoenaed documents, was found guilty and sentenced to 10 days imprisonment.[5] MacCracken filed a petition of Habeas Corpus in federal courts to overturn his arrest, but after litigation, the US Supreme Court ruled that Congress had acted constitutionally, and denied the petition in the case Jurney v. MacCracken.[6][7] Presidential pardons appear not to apply to a civil contempt procedure like the above, since it is not an “offense against the United States” or against “the dignity of public authority.”[8]