donald trump's critics are saying this idea is a fantasy. >> governments all over the world have tried building walls, barriers, what do they show us how they do or don't work? >> they have shown us they can work in a limited fashion. more than a dozen locations around the world. yeah, barriers, fences, walls, puts up. let's look at some. israel and the palestinians. there have been big disputes for a long time. israel used many walls around areas where the palestinians live. israel says by putting these up, they managed to cut down on terrorism. palestinians say, you have managed to cut into the human rights. disputes on almost all of the properties. if you go over towards kashmir and look at india and pakistan. working for many years there on a double row of electrified fences. a lot of talk about landmines in between them. again. india says it makes us safer. some pakistanis disagree. of course, probably the most well known zone like this in the world is the demilitaryized zone between north korea and south