Was watching 'Protecting American borders' and CBP official made this Ukranian lady give up her green card. She swore that she was willingly giving up her green card right there at arrivals and green card was taken away. She was allowed in but had to apply for visas in the future. She was married to an American for 18 months, got divorced then went to live in Ukraine. She would visit on a return ticket, stay for a while then go back 'home'. She was coming in again with a return ticket when she got busted. She was told she didn't have US ties, her marriage ended and she hasn't maintained residency.. different circumstances with the conditional green card but it does happen..CBP officers notice these things.