No one, including HOST, has the ability to read private messages. Complete chat transcripts are kept daily with the content numbering thousands of lines per day.
If an S.O.S. has been sent of such importance the transcripts might need to be viewed where only one person has access. If there is evidence of lewd interactions or predatory activities with a minor or other illegal acts, then it might be necessary to report this to the proper authorities. The administration is only interested in seeking relevant parts of the transcripts for these reasons and not interested in any invasion of privacy.