Explainer: How powerful are U.S. Congress subpoenas, contempt citations?

U.S. House Democrats threatened on Thursday to hold Attorney General William Barr in “contempt of Congress” for not complying with a subpoena to hand over an unredacted version of the Mueller report. What does that mean? Congress does not arrest and detain people for ignoring its subpoenas anymore, but it still has significant power to demand witnesses and documents, though it could take time. The contempt citation is a key part of that congressional clout. President Donald Trump, with Barr’s assistance, is stonewalling several inquiries being led by Democrats in the House of Representatives into his administration, his family and his personal business interests.