Dennis Hope, an American entrepreneur, claims that he holds legal rights to property on the moon, and several other planets. And more than 300,000 people have already bought property from him.
Hope staked his claim to the moon 20 years ago, when he sent a letter of ownership to several governments. Since they didn't dispute his claim, and since no law forbids the ownership of planets by private citizens, he feels he has a legal right.
However, some dispute this claim. Martin Juergens of Germany, for example, says that Frederick the Great granted ownership to an ancestor of his in the 1700's, so therefore the moon belongs to him.