Many businesses claim to be able to sell land on the moon, because of a loophole in a 1967 treaty. This loophole was closed before a claim to ownership was recognised, so all such businesses are committing fraud.
Below is the relevant part of Article 11, Paragraph 3 of the 1979 Agreement Governing the Activities of States on the Moon and other Celestial Bodies:
Neither the surface nor the subsurface of the moon, nor any part thereof or natural resources in place, shall become property of any State, international intergovernmental or non-governmental organization, national organization or non-governmental entity or of any natural person.
This makes it clear that businesses claiming to own land on the moon are lying, and by selling it they are committing fraud.