Now I will admit that it has been a few years since I sat in a civics class, so correct me if I am wrong, but I thought that the whole point of the SCOTUS was to either confirm or reject the constitutionality of laws passed by congress? You know, checks and balances and all of that. If this is the case, then there is no reason for the SCOTUS to be referring to other nations laws for any reason. That being said that would mean that the last legitimate case to be heard before the high court was D.C. vs. Hellar.
Look, let me say up front that I'm not making an argument about should or shouldn't I'm just reporting facts, so don't shoot the messenger. The thing about SCOTUS is that it is in the business of both making law and rewriting the constitution. This what happens every time it rules. The Court effectively says "The constitution means This" and so mote it by. As Holmes ( I belive) said "The court isn't final because it is infallible, its infallible because its final". If you want to be a cynic (and give Al Gore some comfort) you can say that the greatest constituional principle we have is that 5 is a bigger number than 4. The fact is though, that its worked pretty well so far, with a few exceptions.
The thing people need to understand is that the Court makes law and rewrites the constituion because it has to. To give the Con Law 101 answer, in an ideal world the court takes cases for 3 reasons (none of them having to do with seeing justice done). These are
1 Dealing with an issue where the circuit courts are in conflict
2 dealing with a new issue like abortion or the internet or what NAFTA obligations mean for state law
3 A clear constitutional question like whether the right to habeas corpus applies only in the US or to anyone held in US custody
In settling these issues the justices look for guidance from statute law, the constitution and from precedent. If those don't provide clear answers they go looking further afield, the Federalist Papers, state law, political consensus and yes international law. The thing is, the Courts job is to come up with a rule that lower courts can use to deal with similar cicumstances. If they'res nothing here they'll outsource over seas and they've been doing it since John Marshall and the first SCOTUS. Hope this was helpful.
FQ13