Well, then the next step in discerning its definiton is to read all writings about the topic contemporary to that time period. Read about what exactly LED to that proviso. Like other early American terms and words, its meaning for the founders can, and most likely has, been determined.
That's a very well-trodden step. Searching FR alone would provide a mountain of set legal precedent, the John Jay letters, the Law of Nations, etcetera. You've got some catching up to do.