USA: Registered Alien Status

Is this the same as “obtaining a greencard”?

Reason I’m asking, is because my Nephew wants to join the US Army. Problem is, he is a) Canadian and b) lives in Canada. Though because non-us citizens have and do serve in the US Army he holds out some hope. However, one must be a “registered alien”.

The problem I see with this is that to obtain a greencard you need to be a refugee/asylee, have family ties or be sponsored by an employer.

Now the first two he does not qualify for, so presumably he would have to get an employer to sponsor him… then stiff that employer and enlist? Unless for some reason the army will sponser greencard applicants?

If anyone can shed some light on this it would be appreciated. I’ve checked the INS and army websites extensively and I can’t make sense of it all.