Universities, public and private, get away with all sorts of stuff other businesses can only dream of.
Consider the case of a student being kicked out of student housing for "violation of rules". Chances are the student would not get very far with "I will stay until a court orders me evicted and, if you lock me out or deny entry in the meantime, you and not I will have the more serious legal problem. Once you finally get me out, you must hire a state licensed "eviction mover" to put all my possessions into storage, and pay the first month's rental fee on that storage, plus the cost of moving it into storage".
Now, just imagine in a landlord decides a tenant in non-school housing has "violated rules" and wants the tenant out immediately (after, of course, holding a "landlord's tribunal" instead of a housing court eviction proceeding) and instructs landlord's security staff to forcibly eject said person from the property if he shows up.
While the concept of locos parentis has gone by the wayside with the legal age technically being 18 for most things other than alcohol or gun licenses, colleges still continue to act with a relative degree of impunity when it comes to asserting a de-facto exemption from may of the legal protections allegedly afforded to patrons of all businesses.