House Judiciary Committee Democrats voted Wednesday to hold Attorney General William Barr in contempt of Congress, citing a refusal by the Trump administration — which has asserted executive privilege — to provide lawmakers with an unredacted copy of special counsel Robert Mueller's report.

But what does holding someone in contempt of Congress mean? Here are the answers to five key questions about the concept.

1. What is contempt of Congress?

Congress can vote to hold a person "in contempt" if that person refuses to testify, won't provide information requested by the House or the Senate, or obstructs an inquiry by a congressional committee.

Congress' power to hold someone in contempt may be used to "coerce compliance" with its demands, punish a person or remove an obstruction to the inquiry or proceeding, according to the Congressional Research Service.

The authority is not specifically laid out in the Constitution, but it is considered an implied power of Congress, according to the CRS. Congress can pursue a criminal or a civil contempt citation.

Under a rarely used doctrine known as "inherent contempt," the House or the Senate could send members of its security force — the sergeant at arms — to arrest and detain the witness. This power, however, hasn't been used since 1934, when William MacCracken, a former member of President Herbert Hoover's administration, was arrested and held under a warrant after he declined to appear before the Senate. According to The Washington Post, the Senate sergeant at arms did not have a place to hold MacCracken, who was later put up at a nearby hotel.

2. Who has been held in contempt?

When Republicans controlled the House in 2012, they voted to hold President Barack Obama's attorney general, Eric Holder, in contempt over the administration's refusal to turn over documents related to the Fast and Furious gun-walking scandal.

The Obama Justice Department would not prosecute Holder, resulting in a protracted legal battle; it wasn't until January 2016 that a federal judge ordered the Justice Department to produce some documents. The Obama administration appealed, and the case lingered until President Donald Trump took office. Whilethe Trump Justice Department agreed to release some records in March 2018, the litigation was finally resolved only Wednesday after both sides ended a dispute over some of the judge's decisions.

In 2008, a Democrat-controlled House voted to hold President George W. Bush's former White House counsel Harriet Miers and chief of staff Josh Bolten in contempt after the White House, citing executive privilege, directed them not to comply with subpoenas for documents related to a congressional investigation into the firing of several U.S. attorneys.

The speaker of the House asked the U.S. attorney in Washington, D.C., to pursue the matter, but the federal prosecutor declined, citing a Justice Department policy of not prosecuting a White House official for criminal contempt of Congress if that official had invoked executive privilege at the behest of the president.

Congress sued, and a district court judge sided with lawmakers. The Bush administration appealed, and while the case was still pending, Obama took office. The new administration then settled the case, granting Congress access to some of the documents it sought and allowing sworn testimony from Miers. By then, a year and a half after Congress issued the subpoena, the oversight issue largely was moot.

Other Cabinet-level or senior executive branch officials cited for contempt in recent history include Secretary of State Henry Kissinger and Commerce Secretary Rogers C. B. Morton in 1975; Health, Education and Welfare Secretary Joseph A. Califano Jr. in 1978; Energy Secretary Charles Duncan in 1980; Energy Secretary James B. Edwards in 1981; Interior Secretary James Watt in 1982; Anne Gorsuch Burford (Supreme Court Justice Neil Gorsuch's mother) and Attorney General William French Smith in 1983; White House Counsel John M. Quinn in 1996; and Attorney General Janet Reno in 1998.

3. How does it happen?

After members of the House Judiciary Committee concluded their markup discussion over the resolution to hold Barr in contempt Wednesday, the panel voted on the resolution. The resolution now could go to a vote in the full House.

Only a simple majority is needed to advance the contempt resolution, and only one chamber needs to approve the measure for a person to be prosecuted for contempt.

With a criminal contempt citation, the House would refer the citation to the U.S. Attorney's Office for the District of Columbia, which can seek an indictment from a grand jury. All federal prosecutors, including all 90-plus U.S. attorneys, work for Barr, however, and would be under no obligation to pursue a contempt charge.

With a civil contempt citation, Congress would basically sue Barr in district court.

4. What comes next?

Now that the Judiciary Committee has approved the contempt resolution, the full House could vote on the measure, with the timing of that up to House Speaker Nancy Pelosi, D-Calif. Speaking at a Washington Post event Wednesday, Pelosi said that the attorney general "should be held in contempt," something she had declined to weigh in on as recently as Tuesday.

Although a criminal contempt citation could be referred to the U.S. Attorney for the District of Columbia, federal prosecutors would be unlikely to pursue charges against their boss. The contempt resolution is unlikely to result in any substantive action against Barr given the recent history of how contempt charges have played out in the court system.

Contempt of Congress is technically a federal misdemeanor, and if prosecuted, Barr would technically face up to a $100,000 fine and a one-year sentence in federal prison, although both outcomes are highly unlikely.

Congress also has the option to pursue a civil contempt citation from a judge. The Judiciary Committee, for example, could sue Barr in district court, provided that a simple majority of the full House voted to authorize such an action.

"If the individual still refuses to comply, he may be tried by the court in summary proceedings for contempt of court, with sanctions being imposed to coerce their compliance," the Congressional Research Service said in a 2017 paper.

5. How did we get here?

On April 19, committee Chairman Jerrold Nadler, D-N.Y., issued a subpoena for the unredacted Mueller report and key underlying evidence, giving the Justice Department a May 1 deadline to comply. The same day, Nadler and other top Democrats rejected a limited offer from Barr to allow 12 members of Congress to view a less-redacted version of the report in person but prohibit them from discussing it with other members of Congress.

On May 1, Barr sent a letter to Nadler explaining his reasons for not submitting the report. The attorney general was scheduled to appear before the House Judiciary Committee the following day but declined to appear.

On May 3, Nadler wrote Barr asking him to make a good faith effort to comply with the subpoena by Monday. That deadline was missed, and the same day, the committee announced a markup of a contempt citation for the attorney general. Later that day, the Justice Department proposed a meeting with the committee Wednesday to negotiate "an acceptable accommodation" on access to the full report.

But on Wednesday, Trump asserted executive privilege over the report, and the committee initiated contempt proceedings against Barr. The Justice Department had told lawmakers Tuesday ahead of the session that it would recommend that Trump assert executive privilege to that material.