Immigrants taken to the US by their parents as young children grow up as Americans - but on paper they remain foreigners. This means they can be deported if they commit a crime, and condemned to a life of permanent exile.
Sam's first memory is riding a sledge in the snow on the way to primary school in New Hampshire.
His favourite film is Scarface and in breaks during our conversation, he raps Tupac lyrics. He loves skateboarding and going to the gym.
There are millions of American 20-somethings just like Sam but unlike them, Sam can never set foot in the US again.
Two-and-a-half years ago, Sam was deported from the US to Cambodia, a country he had never even visited before.
Wow. Hard to imagine being taken to a country you've never visited, where you don't speak the language, and where you have no money - for stealing a car stereo a few years before when you were a kid.