Simplify the following text for a Grade 10 native English-speaking person.
Original: In correspondence with the governor-general 's office , Casley was inadvertently addressed as the `` Administrator of the Hutt River Province '' which , under the application of Royal Prerogative , makes this recognition binding on all courts .
Simplified: In letters with the governor-general 's office , Casley was called the `` Administrator of the Hutt River Province '' by mistake . The Royal Prerogative , makes this recognition binding on all courts .