Non-students and students not enrolled in class may be removed permanently without formal review because they have no right to attend the class without the instructor's permission. The police will investigate the threats, warn the intended victim, and determine whether the individual is dangerous, has committed a crime, or needs medical help.
Permanent exclusion requires formal review through disciplinary action or academic channels.
The UC Davis student disciplinary process provides sanctions that range from official warnings and reprimands through suspension and dismissal.