I would say two things here
1) University's DO need rules that are in addition to the law of the land and they do need some means of enforcing them. It's not a crime to cheat on an exam (for example) but university's rightly need to be able to apply sanctions to pupils who do that. Students behaviour in university buildings, in tutorials, lectures etc. needs to be monitored and there need to be sanctions applied for students who break those rules. If you were to call your lecturer a **** mid lecture, that wouldn't be a crime but rightly the university needs to be able to apply sanctions to students who do that.
On point 1) I don't think anybody disagrees with the need per say for university's to have their own disciplinary procedures. There's a clear point that simply having students obey the law isn't enough.
2) I don't believe it IS reasonable for university's to punish their students for crimes and I CERTAINLY don't believe it is reasonable for university's to run investigations into crimes (a panel of academics of random disciplines is hardly who you want running a criminal investigation, that's not their specialism) My view might be more extreme than most but it is my view that crimes should only be investigated and punished by the justice system. Reason fro this is that the whole point of the courts, prisons etc. is that we defer to them the power to determine guilt and punish crime. We don't have the right to add our own additional punishments on top. If somebody is tried and convicted of rape and is sentenced to jail, I do not have the right to punch that person because I think he deserves some extra punishment from me. Likewise I don't believe university's should be in the business of applying sanctions for crimes, that to me seems to be an injustice.
Finally, how on EARTH do you know what their motive is for doing this?