Facebook Fan Page Admin, can see the list of people they have Banned and get a provision to unban them.
The ability to Block/unblock users was previously limited to user profile and now have come to the Fan Page, We just happen to notice it.
You can access this feature by clicking on
then select UNBAN and you will see the list of people you had banned. Just go ahead and hit the unban button to the user you want to Unban.
I hope this was helpful