[Freak_NL]

> If a country sells an island, they surely also sell any claims to sovereignty too.

That is a question a judge can answer differently depending on the circumstances of the deal. Was the buyer informed correctly about the consequences? Was the deal made under duress? Was the buyer legally mandated to perform the sale?

The diplomatic cable mentioned in ElReg's article is illustrative of the kind of circumstances the deal was made in:

https://en.wikipedia.org/wiki/File:Diplomatic_Cable_signed_b...