The Framers of the US Constitution used many sources during the development of the Constitution. If you are referring to Vattel's Law of Nations, it too was one of those references.
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Vattel’s work is based on civil law, not English common law as was (almost) universally used in the colonies.
Occam would agree that a legal term when used by attorneys educated in a particular system of law is most likely to carry the definition of that system of law.