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.
With that, would you agree the Constitution is a contract between the states and not a piece of legislation?
You can see where I am going re rules of interpretation.
I have to run, but I look forward to your response.