you've heard the saying, there goes the neighborhood. Well, imagine watching folks move into the beautiful home right across the street. The problem is, they didn't pay a cent for it. The $2.5 million... See More
you've heard the saying, there goes the neighborhood. Well, imagine watching folks move into the beautiful home right across the street. The problem is, they didn't pay a cent for it. The $2.5 million mansion we're talking about. And when neighbors called police, a rude awakening. They couldn't get them to leave. Dan harris takes us to the neighborhood. Reporter: Boca raton, florida. A city synonymous with conspicuous consumption, designer clothing, designer tocks and bombastic boats. Welcome to the aptly named golden harbor drive, where everybody's backyard is right on the water. Rocking the infinity pool. Pretty good look. It is a tony enclave that not long ago played reluctant host to a strange and uninvited guest. This is it right here. Shortly before christmas mike avirom noticed something odd transpiring at a house on his block. This is a sweet house. It's a $2.5 million, 7,500 square foot mansion. The previous owner had money problems, signed it over to the bank of america and moved out. Now, a stranger is moving in without paying a penny to the bank. And he's not alone. Guys pull up and move into this beautiful house and tell you they are establishing an embassy. An embassy for their mission. Reporter: A religious mission? They're going to have transient families coming in and out in accord with their ministry. Reporter: And your response to this was? I don't think that's going to fly. Reporter: It gets even weirder, quickly. The new occupant posts paperwork on the house, saying that nobody can enter without an invitation and two types of i.D. On the elaborate forms, the name of the man who now claims ownership, andre barbosa. Neighbors google him right away and up pops the facebook page of a 23-year-old brazilian, an aspiring hip hop artist who calls himself "loki boy" after the norse god of mischief. That's when neighbors call 911. They've changed the locks, they've put a no trespassing sign out and they're moving in. All right, I'm going to have an officer dispatched as soon as possible. We called the police on these right here. Squatters, they're just defiant. Reporter: The cops show up and speak to loki boy, who you can see right there on a neighbor's secell phone video. But here's where what seemed like a clear-cut trespassing gets truly crazy. Loki boy presents the police with this document, which stops them in their tracks. Loki boy is claiming something called "adverse possession." The notion is that someone can move onto a property, fix it up, take care of it and after a period of time, it's their property. Reporter: It is an obscure but very real law that is on the books in all 50 states. If loki boy stays for seven years, the mansion is his. So, this kid was pretty clever. Because he was using language that was very confusing for you and your force. Absolutely. Reporter: Thus begins a bizarre stalemate with loki boy occupying the house day after day. Police, prosecutors and the bank are in a state of confusion and paralysis. In fact, at first, the bank denies even owning the house. Which is a lucky break for loki boy, who, meanwhile, is living large, working on a new rap video with the mansion as a backdrop. Was that frustrating for you? Very. Reporter: Lynn houston, a nervous next door neighbor, has had enough. I was going to do anything to get rid of him. Anything. Reporter: You were willing to buy that house -- yes. Reporter: You were going to take out a mortgage -- no. Reporter: Just pay cash? Yes. Reporter: Pay cash for this house to get this kid out? Yes. Neighbors outraged to find out a squatter -- Reporter: When he phone calls to the bank are not returned, she alerts the media. Hard to believe but true story out of florida. Reporter: The story goes national. This guy is making it his home for free. Reporter: Meanwhile, the nervous neighbor is convinced that the nightmare here on golden harbor drive is connected to something much larger. I believe there's somebody much more important, much higher, much w, behind him. Don't know who. Reporter: We decide to do some digging. Remember those weird documents loki boy posted on the front of the house? There is another name on there. james McBride. Who, as we learn, is the founder of a mysterious group called "divine province." We can take back all this property that has been taken from us. Reporter: Mcbride is an ex-con who has done time for cocaine importation and run-ins with the irs. He safes he hasn't paid federal income taxes in 26 years and claims he can teach you how to live like him. McBRIDE IS VERY SUSPICIOUS OF The media, but he agreed to speak exclusively with abc news. What is your connection to andre? He's a member of the divine province. Reporter: He says he didn't know in advance about loki boy's mansion takeover, but he now supports him fully. Report It's lawful to move into a house that's not yours and say, this is mine. Correct. Reporter: But there are many OTHER laws McBride feels he and his followers are not subject to. How? He shows me a seal he says was a gift from pope benedict himself. What can you do with this? It means I can now give orderers or issue decrees that the vatican and the roman must follow. Reporter: Yare you saying you have papal authority here in north america. In the globe. Reporter: In the globe? Correct. Reporter: You have primary control of the earth? Correct. Reporter: That seems like a lot of power. I understand. It is. And a lot of responsibility. Reporter: This may sound ridiculous, but the fbi is not laughing. There are an els mated 300,000 people in this country who share SOME VERSION of McBride's belief that american laws do not apply to them. Some of these people are using tactics like adverse possession to take over vacant homes. This one right here has been claimed by a guy named paul dellatore. We found examples all over south florida. All you have to do is file a little bit of paperwork and, bingo, this becomes your backyard. And it's not just florida. This is happening all over the country, with people moving into empty mansions would paying a dime. Why did you decide on this house? Why not? It's a beautiful house. Reporter: Meanwhile, back on golden harbor drive, fully aware of this situation now, nervous neighbor lynn houston o again takes action, hiring offduty cops to watch loki boy's mansion. Some people are sleeping, some people can't eat. Reporter: Just two days later, with media attention reaching a fever pitch, the cops mount a raid. Showed up here, opened the door, walked in, no one's here. Reporter: They haul away loki boy's stuff and change the locks. 51 days after it began, the nightmare on golden harbor drive ends with a whimper. Loki's house of cards has tumbled down. He has sneaked off quietly. The home is now back in the handles of its rightful owner, the bank. The neighbors, however, have not heard the last of loki boy. Days later, he officially releases this music video, where he is seen dancing with his mother against a backdrop of the mansion on golden harbor drive, which, by the way, has now been sold, legally. I think the whole neighborhood feels safer. I feel resolve. We'll sleep better tonight. Reporter: If anything good has come out of this ordeal, the neighbors say it's that they've grown much closer. They throw a victory celebration, complete with a surprise guest. Hey, loki, come on out.
This transcript has been automatically generated and may not be 100% accurate.