回复：朋友持绿卡入境时，被边关警察警告，这是你最後一次持卡入境，然後把绿卡还他。

这是警察唬人，不让他再来回跑绿卡吗？
-No 警察唬人. If he does not have reentry permit, he will not be allowed to enter US next time and his green card will be take away and cancelled. The green car dis for him to live in US permanently, not be used as crossing-border card.