HI,
You need to use this command under WLAN config.
wlan XYZ <WLAN ID> XYZ
....
client vlan <VLAN ID>
peer-blocking drop
....
no shutdown
http://www.cisco.com/c/en/us/support/docs/wireless/5760-wireless-lan-controller/200071-Wireless-Converged-Access-5760-3850-365.html
Regards
Dont forget to rate helpful posts