• Find a page which you cannot edit / set public labels on.
• Click [edit] to edit the labels
• Enter "these all get rejected except for my:this" and click Add
• Red text appears saying " You are not permitted to add the label 'these' to this page." leaving the input box blank.

The user now has to re-enter and re-try each keyword to see if any others fail. There are 3 things I see needing done:

1. Input box being repopulated with sent data if there is any errors
2. Multiple error checking - dont just stop on the first, error on all the bad keywords
3. More informative errors - like "You are not permitted to add non-personal labels to this page."