Not sure how you mean that but the author is indeed talking in opposition to that growing trend.
The ONLY document that is relevant is the United States Constitution and/or the USSC’s interpretation of it.
Do you agree that if a provision in the Constitution is reasonably susceptible of two or more definitions that the USSC has a role to play in resolving the question?
If so, do you also agree that the court will attempt to determine what the founders intended when they used the term?
If so, do you then agree the court may then find it appropriate to refer to material that was available to the founders when they drafted the Constitution, including any that may have been of foreign origination?
On your last supposition. NO, I do not believe that the USSC need consult or consider outside sources, particularly foreign ones in its determination if a statute, etc. is Constitutional. That’s one of the things I’ve seen from leftist Justices saying they ‘consider other sources.’ The US Constitution is the only document that needs to be consulted here.