Its property of the government, if the island is in the waters of the country. You can buy it from them, they make is available for privatisation (dont know how you say it in english). Then there is this whole island-business.
Lets all put our money together and buy one, and build a huge mansion in it and party all springbreak..
Lets all put our money together and buy one, and build a huge mansion in it and party all springbreak..