Unable to remove list users from mailman

We have an assortment of lists using mailman on Mac OS X Server 10.3.9. One of the lists has some users that will not let us remove them or change their settings. I also tried to remove them from the Mac OS X Server Admin GUI and that didn't work either. So how do I remove them manually if that is possible?

Our primary access to mailman is through the web interface.

Thanks,
Ben