Index: cas.module
===================================================================
--- cas.module	(revision 1467)
+++ cas.module	(working copy)
@@ -142,6 +142,17 @@
       return;
     }
 
+    if (user_is_blocked($cas_name)) {
+      // blocked in user administration
+      drupal_set_message("The username $cas_name has been blocked.", "error");
+      return;
+    }
+    else if (drupal_is_denied('user', $cas_name)) {
+      // denied by access controls
+      drupal_set_message("The name $cas_name is a reserved username.", "error");
+      return;
+    }
+
     // try to log into Drupal
     if ($cas_authmap) {
       // users are coming from Drupal; no need to use the external_load and the authmap