The United States Supreme Court knows that it is more than just the ultimate arbiter of the law of the land in the United States; it also wields influence worldwide. And though the Court regularly explains that issues involving foreign policy are best left to the legislature and executive, it does not rule in a vacuum cut-off from the rest of the world.
Along with the increase in globalization and e-commerce, cases in U.S. courts have increasingly involved foreign parties, requiring U.S. courts, including the Supreme Court, to interpret and consider foreign laws and the impact on U.S. law and individual cases. In addition to decisions of the U.S. Supreme Court having a clear global influence on business and immigration, the High Court has also influenced many foreign tribunals, and been influenced.
Foreign Courts Less Reliant on SCOTUS
Interestingly, a decade ago, prominent lawyer/journalist Adam Liptak, wrote an in-depth report explaining why foreign courts were citing SCOTUS decisions less often. In the post-WWII world, the U.S. High Court was seen as highly influential by the judicial tribunals across the world when it came to matters of civil rights.
Looking at Canada and Australia's High Courts, Liptak found that these tribunals were relying less on the U.S. High Court, and more on judicial bodies like the European Court of Human Rights, and other international constitutional/human rights tribunals. While this might be partly explained by the fact that these tribunals are relatively new (still), Liptak also suggests that part of the reluctance of foreign courts to cite U.S. decisions comes from the international contempt caused by President George W. Bush's foreign policy decisions.
SCOTUS Less Reliant on Foreign Courts
Interestingly, for some time, it has been a hotly debated issue whether SCOTUS should cite foreign law and court decisions, and what sort of impact those should have on decisions in the United States. Former federal appellate justice Richard Posner published a vehement opinion piece (nearly 15 years ago now) explaining that SCOTUS should never cite to foreign decisions as authoritative, or precedent setting, or even in a "nose-counting" effort to find "international consensus" (of course Posner didn't hold back, and even attempted to benchslap the High Court).
Notably though, before retiring from the High Court, Justice O'Connor said:
"I suspect that with time we will rely increasingly on international and foreign law in resolving what now appear to be domestic issues. Doing so may not only enrich our own country's decisions; it will create that all-important good impression. When U.S. courts are seen to be cognizant of other judicial systems, our ability to act as a rule-of-law model for other nations will be enhanced."
Justice Breyer also believes that SCOTUS needs to engage more frequently with foreign judicial systems and practices.
Overtime, it seems Posner's opinion has been gaining more traction as even the U.S. Supreme Court seems to be leaning against citing to, or even accepting the decisions of, foreign tribunals. In a recent unanimous decision, the High Court explained that when considering a foreign law's impact on a case, it need only "respectfully consider" that foreign jurisdiction's interpretation of its own law.