If you ask Dennis Hope, he'll tell you he's the richest man on Earth—in fact, he'll say he's the richest man in the Solar System. Why? Because, as far as he's concerned, he owns most of it.

In the early 1980s, Hope, then unemployed for about a year, thought he'd be a good property owner and could make a living by managing real estate. He looked out the window and saw more unclaimed property than he could possibly fathom—the moon. He remembered a tidbit from a political science course he took in college—the 1967 United Nations Outer Space Treaty said no country could own the moon, but it says nothing about individuals.

Hope wrote a letter to the United Nations saying the moon was his and asked the group to come up with a legal reason why an individual could not claim ownership of the moon.

He never heard back.

"I sent the United Nations a declaration of ownership detailing my intent to subdivide and sell the moon and have never heard back," he says. "There is a loophole in the treaty—it does not apply to individuals."

Since then, he's sold more than 611 million acres of land on the moon. Individual, one-acre lots sell for $19.95 ($36.50 after a "lunar tax" and shipping and handling of the deed) and there are discounts for larger plots. He once sold a "country-sized" plot of land—2.66 million acres—for $250,000. He's sold plots on the moon to three former presidents (George H.W. Bush, Jimmy Carter and Ronald Reagan). He's president of the Galactic Government, a democratic republic that represents landowners on the moon and some of his other properties (he claimed Mercury, Mars, Venus, Jupiter's moon Io, and Pluto while he was at it). Customers can buy the entirety of Pluto for $250,000.

According to Tanja Masson-Zwaan, president of the International Institute of Space Law, the United Nations never responded because the treaty applies to both countries and its citizens, she told National Geographic.

"What [Hope] is doing does not give people buying pieces of paper the right to ownership of the moon," she told the magazine in 2009. Nonetheless, Hope continues to sell acre plots on the moon seemingly unabated.

Hope and other moon-fanatics are the subject of the new documentary "Lunarcy!" which follows people who have dedicated their lives to Earth's only natural satellite. There's Alan Bean, an astronaut-turned-artist, who paints moonscapes and imprints them with boots he wore when he became the fourth man to walk on the moon; Christopher Carson, a 20-something Texan who is determined to become the first man to leave Earth, move to the moon, and never return; and Hope, who still hasn't figured out how to turn the moon's "Delta" currency into American dollars, but has made a small fortune selling the moon nonetheless.

Director Simon Ennis says the moon is "so blatant and visually striking, so obvious in the night sky," that people are drawn to it. When he first heard about Hope's business, Ennis says he thought "it was the greatest idea anyone has ever had."

"I think it's an unbelievably smart and hilarious idea. He has a sense of humor about what he does, despite the fact that he is absolutely serious about it," Ennis says. In the documentary, Hope explains he once received an energy bill from a man who claimed to own the sun. After careful consideration, he says, he decided to ask the man to turn off the sun.

Talking to Hope, his seriousness is immediately clear: He's met with foreign dignitaries and attempted to get his government officially recognized by the International Monetary Fund (so Deltas can be traded for Earth currency in international markets). When China announced they would attempt to encroach on his property by building a moon base, Hope threatened their government.

Hope contends that there is more than $6 quadrillion dollars worth of helium-3 reserves on the moon, and that he and his property owners, of which there are thousands, own all of it. Helium-3 is used in nuclear fusion research on Earth and trades for about $125,000 an ounce.

"When China announced they planned to be on the moon by 2012, we wrote a letter to their president saying we didn't have a problem with it as long as they had a licensing agreement with us. Otherwise, their craft would not reach the moon," Hope says.

He wouldn't say how he planned to stop a country or person from going to the moon.

"We currently can stop any craft we want to from going to our properties," he says. "We have no problem with exploration, but as for anyone building anything of permanence, they don't own the land. That would be like Canada coming down to the United States and building a facility without asking permission. The response from the government would be irate—we would be the same if someone tried to build on the moon."

While he doesn't support others mining the moon, he does realize the historical importance of it. He's set up 23 "celestial reserves" on the moon, including the Apollo missions' landing sites and the two polar regions, where much of the moon's water is stored. In 2011, a group attempted to buy the moon's north pole from him for $50 million, but he declined the offer, he says.

"I verified that they had the money to do it, but we want to make sure people have what is needed for living at an inexpensive price," he says.

"Lunarcy!" has been screened at several prominent festivals, including the Toronto International Film Festival and South By Southwest. It'll be aired for the first time to a wider audience on Epix on April 3. Since the documentary was finished, Hope says sales of lunar plots have increased by about 30 percent.

He says the time is quickly approaching when those owners will be able to take advantage of their land. The Galactic Government is exploring building a pyramid-shaped moon city that would have a roughly two mile by two mile base. He hopes to be the first private citizen to fly there.

"I'm a private pilot, so I'd love to be able to fly the first craft there," he says. "As the elected president of the Galactic Government, one of my responsibilities is to build a city on the moon."