My theory is related to ARTICLE I, SECTION 6, CLAUSE 1 of the US Constitution:
"The Senators and Representatives...shall in all Cases, except Treason, Felony, and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same...."
Since there's a shutdown, criminal members of Congress are subject to arrest. I hope he announces that at least a third of them have been indicted
