We had a similar case in Portland, Maine, a few years back. Eventually the Planning Board issued a permit in response to widespread community support. The neighbor was quite pissed off. Here's a song that I composed to commemorate the struggle:

By Charlie Ipcar © 1992
Tune: after theme song from Beverly Hillbillies'

Treehouse

C---------------G
Ben built a house, high up in a tree,
--------------------C
Ben built a house for everyone to see;
-----------------------F
It had cedar shingles and a plywood floor,
G------------------------G7---- C
Three small windows and a big front door.


Ben built a house for all his friends to share,
They'd play all day, high up in the air;
The birds and squirrels were very surprised to see
Three little kids hanging out in a tree.

But the next door neighbor shook his head and swore,
"The City's gonna hear about this big eyesore!"
Inspector Rowe came by, and a letter soon was sent;
You know, Ben hadn't filed for a building permit.

"You can't build a treehouse without central heat,
A bathroom, a kitchen, or a bedroom suite;
The codes are quite specific," said Inspector Rowe;
"A building is a building, and this one's got to go!"

Now Ben and his family don't know what to do,
Some friends urge compliance, some urge them to sue;
When you're only seven it's so hard to understand,
Why a treehouse in everyone's front yard isn't part of the City's master plan!

The last time I checked the treehouse had been taken down, but it had survived for at least 5 years. No doubt, Ben is now a registered architect.

Cheerily,
Charley Noble