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Same author, different Publisher and 4 years later (same definition):

The royal dictionary English and French and French and English: extracted from the writings of the best authors in both languages
Author: Abel Boyer
Publisher: printed by John Mary Bruyset, 1768
Original from the Complutense University of Madrid
Digitized: Jul 27, 2009
Length: 716 pages
Subjects: Foreign Language Study / French

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The 1768 dictionary can be found here.

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Abel Boyer writes another version, in 1771 (Editor: J. C. Prieur) in which the definition for "Naturel, le", includes "natural" and "native" as well. Found here.

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More proof the founders/framers would have easily "interchanged" native and natural:

The new royal and universal English dictionary ...: To which is prefixed, a grammar of the English language, Volume 2
Author: J. Johnson
Publisher: Millard, 1763
Original from Columbia University
Digitized: Sep 16, 2009

Found: http://books.google.com/books?id=OmtHAAAAYAAJ

Point being, as bushpilot1, RedSteel and other's have shown, the time frame from around Vattel's early editions and the framing of the Constitution...there were MANY resources which used the definitions of Natural and Native (and the French Naturel) interchangeably.