[highball]

Unfortunately the Constitution did not clearly define it, but the founders based it on Vattel’s Law of Nations

No. They did not "clearly" do so. Some Founders speak approvingly of his work, but that is not the same thing.

Vattel also wrote that only elites should own arms. How seriously do you think the Founders took that advice?

[Nero Germanicus]

For example, James Madison, “The Father of the Constitution” spoke of a position on this issue that Vattel would have opposed.

“It is an established maxim, that birth is a criterion of allegiance. Birth, however, derives its force sometimes from place, and sometimes from parentage; but, in general place is the most certain criterion; it is what applies in the United States. It will therefore be unnecessary to investigate any other.”—22 May 1789, Papers 12:179—82