CCNA 200 301 Security Fundamentals

Whenever you want to control which devices can talk to the main CPU, a CPU ACL is used.
Note: CPU ACLs only filter traffic towards the CPU, and not any traffic exiting or generated by the CPU.
Reference: https://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/109669-secure-wlc.html