I know....that's probably not possible.I say be on the safe side and deport him.
Yes, it is possible. You can be a permanent resident your entire life and not qualify to apply for citizenship. Usually, that invovles a criminal record, but there are other disqualifying factors.
Benkabbou came to the US from his native Morocco in 1987, and was granted permanent residency four years ago. But when he applied to become a naturalised US citizen in 2005 - by which time he was already serving in the army - immigration officials discovered that he had failed to register his first marriage and alleged that the ceremony had been arranged fraudulently to get him into the country.
Benkabbou says that the marriage was annulled and argues it is therefore irrelevant to his immigration status. "I do not think I deserve to get deported after serving honourably during a time of war!" he wrote in an email from Afghanistan.
I'm curious to know whom the bride might be ... and what's Benkabbou doing in Afghanistan, anyway?