1. You can go to configuration> Advanced Service> All Profiles and Delete it.
2.
(3000) #configure terminal ap ap-blacklist-time 0
(3000) #stm add-blacklist-client 00:00:00:11:22:35
(3000) #show ap blacklist-client
Blacklisted Clients
-------------------
STA reason block-time(sec) remaining time(sec)
--- ------ --------------- -------------------
00:00:00:11:22:35 user-defined 910 Permanent
In the example, the ap blacklist-time was zero, meaning permanent, but you can change it in seconds to whatever you want.