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: 
For one-worders, I like @Robusto's "self-important" and @Nick's "presumptuous."

I'll add "inconsiderate," since I don't see that it's been added yet.

I've also described people with similar tendencies as "having an unjustified sense of entitlement," though I usually leave out "unjustified." 

"scofflaw" is a fine word, but it's almost an archaic usage. I just haven't heard it in non-facetious, non-ironic usage in USAmerican language. 
"bumptious" falls into this category as well. Nothing wrong with the word, but not used much. It can be used. Maybe you'll use it and start a trend. Of course then it might become a cliché .

"sociopath" is probably the correct diagnosis, and so has the advantage of being literally correct. Probably a bit inflammatory (unless you mean to be inflammatory, in which case, have at it).

I don't feel "loose cannon" is correct here, unless the OP has a different sense of the person in question than I'm getting. Usually a loose cannon is someone who is institutionally entrenched and whose character is endangering either the institution or those it comes it contact with.
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.)