Tom,
What are you using for your RADIUS server? What type of authentication are you using on the WLAN?
802.1X will block the clients from sending traffic on the network until they are properly authenticated. So, you shouldn't need to modify the firewall to allow/deny them. If you are trying to restrict access after authentication, it may be easier to do that based on some other trigger other than MAC address. The best method would probably depend on the specifics of what types of devices you are trying to restrict and what you are trying to restrict them from doing.