"Trump has made illegal immigration the foundation of his campaign, but Melania was almost certainly working in the US illegally. And every time she returned to the country and passed through immigration she would have had to have committed fraud by saying she in the US to visit rather than work. In theory this would make her subsequent Green Card and even citizenship suspect, based on visa fraud earlier in the process."

http://talkingpointsmemo.com/edblog/was-melania-trump-an-illegal-also-argh