Unless it's set up somewhere else and then once tried at home again it wouldn't work?
But it's not the reason anyway, sorry for the confusion 
A person who has been banned could sign up again at a different location (thus a different IP address), and an unknown email address & username (we ban on email, username & IP to be thorough & some other methods not to be disclosed
). If that person then returned to the location at which they were banned (usually home) then they would instantly receive a "Ban" message when they attempt to log in....the new account that had been set up however would not be deleted by the system, but it would now be linked back to the original IP address and as such rendered useless.
