On the issue of the citation of foreign law in United States Supreme Court opinions, I think this is the key passage in Adam Liptak’s recent article:
The controversy over the citation of foreign law in American courts is freighted with misconceptions. One is that the practice is somehow new or unusual. The other is that to cite such a decision is to be bound by it.
Even conservative scholars acknowledge that American judges have long cited decisions by foreign courts in their rulings. “The Supreme Court has been doing it for basically all of our history, and with some degree of gusto,” said Steven G. Calabresi, a law professor at Northwestern and a founder of the Federalist Society, a conservative legal group. Professor Calabresi said he generally opposed the citation of foreign law in constitutional cases.
Judicial citation or discussion of a foreign ruling does not, moreover, convert it into binding precedent.
So, first of all, the practice has been a banal one going back to at least the Marshall Court. And even more importantly — as even several of the conservatives working themselves into a foaming-at-the-mouth outrage about this banal practice seem to concede in the course of the article — the idea that references to foreign legal precedents actually affect Supreme Court holdings in any significant way is exceptionally implausible. Nobody’s vote in Roper would have changed if there was a norm against referring to the law in other nations. So who cares? In a nice article unfortunately not available for free online, Mark Tushnet correctly notes that this silly controversy is about the culture wars, not about law.
I think it’s also worth addressing this:
At their confirmation hearings, Chief Justice John G. Roberts Jr. and Justice Samuel A. Alito Jr. indicated that they were opposed to the citation of foreign law in constitutional cases. Chief Justice Roberts noted that foreign judges were not accountable to the American people and said that allowing the use of foreign precedent expanded judicial discretion.
“Foreign law, you can find anything you want,” Chief Justice Roberts said. “Looking at foreign law for support is like looking out over a crowd and picking out your friends.”
This argument (borrowed from Scalia) has the obvious problem that it’s equally applicable to any data source or method of interpretation. Certainly, it’s true of originalism: between the multiplicity of historical sources and the ability to define constitutional principles at different levels of abstraction a judge can virtually always identify friends which confirm her ex ante preferences, and in those rare occasions where this isn’t possible Scalia et al. will just ignore the evidence anyway. Scalia’s agrument that courts shouldn’t refer to legislative history has the same problems. Of course, legislative history can be misleading, but since this is true of any source of evidence it’s not clear why it’s useful to rely on a smaller number of potentially misleading sources of evidence.