When configuring an Access Control List (ACL) to restrict traffic to the Wireless LAN Controller (WLC) CPU, the direction of the traffic is crucial. Since the ACL is meant to control traffic that is destined for the WLC CPU, it should be set as "Inbound". This means that any rules applied within this ACL will affect incoming traffic towards the WLC, which is necessary when aiming to restrict certain types of traffic from reaching and potentially overwhelming the controller's processing capabilities.