Have a read through this thread, you will need to setup Group authentication in LDAP (or us a specific LDAP Attribute to allow or prevent access).

http://lists.freeradius.org/pipermail/freeradius-users/2010-October/msg00058.html

On Wed, Nov 17, 2010 at 1:55 AM, eduardo moreira <eduardomoreirars@gmail.com> wrote:
Hi,
 
With help of list i make my freeradius + ldap, now works.
 
But now i have other doubt, how to disable one user to authenticate in freeradius?
 
Remember, i dont block user to log in ldap, but block user to use freeradius.
 
Thank for help.

-
List info/subscribe/unsubscribe? See http://www.freeradius.org/list/users.html