This would have negated any issues that Princeton's networks were seeing. Properly configured, the only impact would've been that offending DHCP clients would not be able to use the network until they get a proper DHCP lease. There'd be no manual banning or need to contact your user. The user would probably contact you. All of the major networking hardware manufactures have some flavor of it: Cisco, HP, even Juniper claims to. I'd imagine the Princeton network uses something that would support this feature. *The particular related technology in Cisco world is "IP ARP Inspection".