What you want, to the court system is irrelevant. The practice of citing internation law dates back to before the Warren court. What my point was that in your words, they do "construe law in light of the US Constitution" but in addition to that, provide other places that do the same thing they are arguing. The slippery slope, to continue the...well, its become flat because it is done in almost every single court case and is now common practice.
The function of the court is to read the law that has been enacted by the elected representatives in the the various legislatures and to apply that law, and no other, to the to the matter at hand. Irrespective of the merit of the motives of the Justices, they are sworn to uphold the Constitution of the United States. This, in no way, includes 'seasoning' their decisions with the 'spice' of laws which have been enacted in foreigh nations.
Let's say there was an argument you were having with a friend over say...would you not use evidence that you could use just because it was say...in another state? In the emerging global economy and worldview, sometimes, and the court usually uses it, international law can be used to supplement a judgement, but at the same time using on the constitution as the main basis for their arguments.
Your hypothetical construct is just that, a hypothetical construct.
The point is quite simple. Unadulterated U.S. law for the U.S.
In an effort to ameliorate the conditions which have led to frequent wars as far back as one can trace, and to reduce economic tensions, the countries of the European continent have decided to emulate the United States of America and form their own "United States of Europe" which they have decided to name, The European Union.
It would seem that rather than our bending to the laws, customs, and the like, to those of the EU members, things should be the other way round. That is, unless, of course, you believe that the U.S. should be seeking membership in The European Union.