They usually install print metering software just for this reason.
Did you revoke printing rights for the offenders?
Did you publish a policy?
and the system they use is at:
Another is at http://www.printaudit.com/
We recently set up 6 network printers in our school for faculty. Now they print hundreds of copies each day of personal materials. Is there a method to allow users on a network to print only a certain number of pages per month or semester under their login, and after they hit that number, the printer will not respond to their print order. Our server runs Windows 2003. The workstations run Windows 2000 and the printers are Brother Hl 5170DN.