as far as the contract issue, no they cant do antying to jeopardise his green card. green card is filed on a basic of a job offer not a job contract. beside that, it depends on what the contract says, as to waht is gonna happen, if he quits his job before the contract is over. i am not sure, but from my understand, if the contract was made before he got his greencard, then its should be nullified, coz before the contract he wasnt a legal us resident allowed to work, so the contract shouldnt hold good in court. like i said, i am not sure though, i dont know the contents of the contracts, but his green card is safe.