Actually, I beg to differ. Check it (the Constitution) out yourself.

When it comes to the US Constitution, the restriction of having to be a "Citizen" chiefly had to do with who could hold office, and not much more, other than in general terms.

The framers' intent and wording, particularly with respect to the rights protected by the Bill of Rights (the first 10 Amendments), deliberately avoided the use of such a term as "Citizen" — instead intentionally using the terms "people" and "person" when defining those rights. This was in the same spirit as the Declaration of Independence ("all men are created equal..." etc.). The American Republic was supposed to be a place were human rights were universally recognized, regardless of civil status.

But like I've already said in this thread, the folks in Washington pay no mind to the country's "law of the land" (see paragraph 2), preferring to invoke their own administrative law instead.