I include in my "policy manual" the following

Modifying a List's Archives 
The messages of some lists are archived for reference purposes. These archives will not be altered in any way by LISTSERV Administrator. Requests to make an exception to this policy will be considered, but granted only when it can be compellingly demonstrated that harm to the University, Institute, Project, or members thereof will be avoided by doing so. Any decisions regarding modification of the archives is at the sole discretion of the LISTSERV Administrator.



Regards,
Randy Klumph
Teaching Research Institute
Western Oregon University