The Law of Nations and the US Constitution

The United States Constitution in Article I Section 8 states that the Congress has the power:

To define and punish Piracies and Felonies committed on the high Seas, and Offences against the Law of Nations;

US Constitution from Article I Section 8 (click to enlarge)

Some have gone so far as to say that the phrase “the Law of Nations” is a reference to Emerich Vattel’s work commonly known by that name. I think most would find that silly, but let’s look closer.

• It must be a citation because it is capitalized. FALSE. Every noun in the Constitution is capitalized, so capitalization here implies no special meaning. Add to that the fact that “the” is not capitalized; a citation should read “The Law of Nations” not “the Law of Nations.”
• But it is still the title of de Vattel’s book. FALSE. The title of de Vattel’s book was Le Droit des gens ou principes de la loi naturelle appliqués à la conduite et aux affaires des Nations et des Souverains. “The Law of Nations” isn’t even the full English title.
• But it is still the title of de Vattel’s book. FALSE. Look at the Constitution again, at the larger phrase: “Offences against the Law of Nations.” Guess what? That is the title of Chapter 5 of  Blackstone’s Commentaries on the Laws of England, the most influential legal treatise of the time. I would say that if anything, Blackstone has the stronger claim than Vattel.