Lawyer Barnes cannot sue a congresswomen or men for defamation. They have immunity under federal law.
When the Covington students accept the invitation to the WH, they have to encourage POTUS to open up Libel Laws.
Listen to what attorney Libby Lock has to say in Tucker Carlson interview:
https://youtu.be/wyYwrdLcRnM?t=817
(start at 13:37)