Before contempt
The subpoena and question must be lawful and pertinent, the refusal must be willful, and any Fifth Amendment claim or other privilege must be evaluated. A valid privilege is a defense; Congress cannot punish a witness merely for properly invoking it.
Criminal contempt of Congress
A committee may report contempt and the Senate may certify it to the U.S. Attorney under 2 U.S.C. §§ 192–194. The statute provides a misdemeanor carrying one to twelve months’ imprisonment and a $100–$1,000 fine. The statute says the U.S. Attorney must present the matter to a grand jury, but the executive branch has long asserted prosecutorial discretion. DOJ may decline, investigate, seek an indictment, negotiate compliance or prosecute if the evidence and law support it.
Civil enforcement
The Senate may authorize a lawsuit asking a federal court to declare the subpoena valid and order compliance. If the witness then disobeys the court order, the court may use coercive civil-contempt measures—potentially fines or detention—until compliance. The objective is to obtain testimony or documents, not punish the original refusal.
Inherent contempt
The Senate also possesses a rarely used constitutional power to have its Sergeant at Arms take a witness into custody, conduct a proceeding and detain the witness to compel compliance, generally no longer than the congressional session. Neither chamber has initiated this process since 1935.
Other possible referrals
Congress may refer evidence of other suspected federal offenses—such as perjury, false statements or obstruction—to DOJ. DOJ independently decides whether to investigate or charge, and any charge must be proved in court.
Fauci pardon warrant ↗Fifth Amendment doctrine ↗CRS on subpoena enforcement ↗2 U.S.C. § 192 ↗2 U.S.C. § 194 ↗