You want to know where Vattel is in the Constitution....???
It's in the penumbras.
See Roe v. Wade.
Yes. Not to put too fine a point on it. I want you to show me where the Constitution cross references “Vattel” or the “Law of Nations”. So far all I’ve been shown is that Vattel is “in” the Constitution the same way that the “right of privacy” is “in” the Constitution: by penumbral construction.