The University and all universities and colleges have established and codified rules of conduct for students.  Punishments, up to and including suspension or expulsion, are part of that system.  Such punishments may be applied to students whose behaviors are not "criminal".....for example, cheating on a final exam is not a 'crime'.  However, in most universities it will lead to severe punishment.  There are also behaviors which violate BOTH university conduct codes and criminal laws.  In such cases a student might be punished by both the university (for the code violation) and the criminal courts (for the criminal violation).  

The circumstances leading to a suspension or expulsion may NOT meet the standards set for criminal prosecution, this does NOT mean the university can't discipline the student for a code violation.  This seems to be such a case. However, at least as I read the story, the university did NOT correctly follow its own discipline code policies and procedures.  GCrum