[0xfaded]

I have to disagree with the idea that it's not a solution, governments refuse to hire foreign nationals all the time and even regulate the private sector through things like ITAR.

Now I agree it's an unfortunate solution in some respects. There are moral issues both utilitarian (1000 Einsteins) and idealistic (all humans are equal). There are also work arounds. For most purposes if you naturalize and renounce your previous citizenship you will legally be treated as a national. ITAR only requires a green card.

Arguing against discrimination in a security context though, when nationality is indeed a reliable discriminant, is difficult.