I think the disagreement here is down to speaking at cross purposes about why the University is allowed to expel its students. The way the debate has been phrased thus far, it seems as if the university simply unilaterally imposes a ‘court’ on its students. However, I think it’s quite easy to solve the conflict when you consider why, in fact, the university, or the employer, who whatever other body, has jurisdiction. It does not have jurisdiction qua private body: a person cannot simply walk up to another on the street and declare that they are a court, and that they wish to hear a case against that other person. Instead, it is because there is a contractual relationship between the university (or employer etc.) and the student (/employee etc.). The contract entitles the student to attend the university, use their accommodation etc. In return, they submit to a number of rules. I remember my contract for university referred explicitly to the founding statute, which prohibited any activity unlawful by the general law (plus a number of additional stipulations, like 'no cheating', 'no plagiarism', 'nothing immoral or improper'), but set up its own procedure for monitoring breaches in this regard. Therefore, the student can be ‘tried’ by the university because, when signing the contract to attend, they agreed to the procedure.