How can websites like moonestates.com sell land on the moon?

If you read their disclaimers, you will find the following:
“One can become the legal owner of an extraterrestrial body, if you are the first one who claimed it, and that is the Lunar Embassy.”

On places like the moon, which no human really ‘owns’ – it easy to sell land with the above mentioned disclaimer. But will it hold in court?

Or best advice is to avoid buying land on the moon – or risk losing the money you invested.