Depending on the Nationals bylaws, any party where several members are in attendence, it is considered a group party.
6 years is a very long time, but, the SAE National must have felt it was worth the effort to sanction them for this long. It is usually for 4 years when all of the current chapter graduates.
If Case Reserve is that important to SAE future plans, I am sure the fine would be overturned as shouldering a new colony there would be insurmountable.
There may have been much more than meets the eye.