Yes, this is what I though too. He just bought property rights. It's still part of whatever country it's located within and they can apply all of their legal code on you. I imaging digging deeper than a few feet would be illegal on that without proper authorization first. Having a really sovereign country is kind of difficult.
If someone who read this get his very own country someday, please name it something that will give you the .gz ccTLD so I can finally buy www.tar.gz where I will offer visitors to download an archive of the Internet :-p.
> Having a really sovereign country is kind of difficult.
No it isn't. All you need is a nuclear missile and you can tell anybody, including US President to piss off. And they will do it. See http://en.wikipedia.org/wiki/North_Korea for details.