function removeAssociation($server_url, $handle)
    {
        if (!$this->active) {
            trigger_error("FileStore no longer active", E_USER_ERROR);
            return null;
        }

        $assoc = $this->getAssociation($server_url, $handle);
        if ($assoc === null) {
            return false;
        } else {
            $filename = $this->getAssociationFilename($server_url, $handle);
            return Auth_OpenID_FileStore::_removeIfPresent($filename);
        }
    }