Explainer: How hard-hitting are U.S. Congress subpoenas, contempt citations?

Congress has significant, if time-consuming, powers to demand witnesses and documents.One of these is the contempt citation.Democrats in the House of Representatives are threatening to use it on multiple fronts, including against Barr for ignoring a subpoena issued by the House Judiciary Committee seeking an unredacted version of the Mueller report on Russian interference in the 2016 U.S. election and President Donald Trump.