I'm not sure this is accurate.
Does anybody know if the government has the power to do this or if it was done to US volunteers fighting for the Brits before we entered the war? I've never heard of such a thing.
I believe there was some kind of “administrative” procedure to state that as long as they wore the uniform of another nation they were not “considered” to be citizens. It all had to do with our supposed “neutrality” and should one of these guys fall into the bad guys hands.
I believe the men that flew in the Flying Tigers were also put into some special “non-citizen” category.
Obviously, once we entered the war this all went away.