Where did you read that he was a resident alien? Chances are he didn't have his papers. Some do, some don't. I know a boy, who happens to have US citizenship, grew up in Ecuador, and came back to serve in the army this year. I don't understand it, but I certainly respect it. People assume he is an illegal because he doesn't speak English well. Those people can get ugly. Fortunately he has a strong character and doesn't let it get to him. I resent all the anymosity towards "illegals". The ones I know are more decent than some "US citizens" who were born and bred here.
If he was a Soldier in the US Army, he would not have been able to enlist as an illegal alien. Resident alien, yes, illegal, no.