When a Supreme Court justice decides a case, should he or she look exclusively to the Constitution and U.S. laws? Or should foreign policies or laws come into play?

Those are easy questions for most Americans. They know U.S. citizens are subject only to laws made by American legislators -- not foreigners at the United Nations, in Europe or in Zimbabwe.

Yet at least one sitting Supreme Court justice says American jurists should look to foreign precedent. And President Barack Obama’s first nominee to sit on the high court, Sonia Sotomayor, seems a bit unclear on that point, too.

Just two years ago a book titled “The International Judge” featured an introduction she penned. “The question of how much we have to learn from foreign law and the international community when interpreting our Constitution,” she wrote, is “worth posing.”

Earlier this year, Sotomayor spoke to the Puerto Rican chapter of the ACLU. “International law and foreign law will be very important in the discussion of how to think about the unsettled issues in our own legal system,” she told the group.

Both quotes are troubling. Quite simply, there’s no need to consider foreign law when interpreting American constitutional law.

For the Constitution is, by definition, all one needs. And despite its brevity, our Constitution is remarkably effective. As a guiding legal framework, it works far better than longer (and long-winded) documents such as the European Union constitution. Our Constitution’s protection of the freedom of speech, for example, is remarkable, admirable and unique.

Unfortunately, Sotomayor isn’t alone in her consideration of foreign policies. Earlier this year Justice Ruth Bader Ginsberg told a panel at Ohio State University that our Supreme Court ought to pay more attention to the laws and policies of other countries. “You will not be listened to if you don’t listen to others,” she warned.

Well, what does it matter whether jurists in Yemen decide to cite U.S. precedent?

Our founding document was written to create a United States. The laws passed in the 221 years since it was ratified were meant to govern Americans. Anyone who wants to live under Sudanese law is free to move. Yet for more than two centuries, the line to get into the U.S. has been far longer than the line to get out. We’re doing something right. Continued...