No one is suggesting to sue. The suggestion is to get advise from a professional, i.e. a lawyer rather to listen to random people on the internet. A lawsuit may or may not follow.
A lawyer supplying helpful information like "Ok, this expulsion was triggered by the Department of Admin, which is overseen by John Smith, who has the power to reverse this decision. Schedule a meeting with him or find office hours to plead your case. I shouldn't get involved outright because it will escalate your situation and be received poorly." is less likely than "I can write a threatening letter and we'll see where it goes". A hammer hammers.