Is it allowed not to stay in US after getting green Card?

來源: 於 2007-07-22 19:12:09 [舊帖] [給我悄悄話] 本文已被閱讀：次

My son need to finish his university study in Canada after he gets his
green card.
Is it allowed for him to leave US and does not have to stay in US at
least 6 months and keep green card.

Thanks