I believe the original intention of that rule was to stop an attempt of swaying a particular vote by arresting congress members who may vote against.
Why, IMO, they want an impeachment on the table. They can use the excuse that they were arrested (if that would happen) because they were going to vote for impeachment.
Only possibility at the moment is to bring the whole fucking thing done by all out DECLAS, AFAIC.
DVS suing Sidney is a bad sign. It means DVS got cover from the tPRB that the "justice system" will take care of any loose ends. Same will happen to any Trump supporter.