Question: I'm trying to write a letter to the editor of my local paper about their report of a man who doesn't think the rules apply to him. Is there a word for this? He's a bit of an egoist, demanding to speak at city council meetings after the public hearing portion of the meeting has been closed.

Answer: 
He's a *loose cannon*:

> 
> an unpredictable or uncontrolled
>  person who is likely to cause
>  unintentional damage.
> 
> 
> 

-New Oxford American

> 
> a person whose reckless behavior
>  endangers the efforts or welfare of
>  others.
> 
> 
> 

-Dictionary.com

(My initial answer was going to be *[maverick](http://dictionary.reference.com/browse/maverick)*, but this led me to *loose cannon* and I liked it better.)
How about *prima donna*, one who thinks the rules apply to others and not them.