must increasingly consider the world beyond our national frontiers. It must consider that world in determining the reach of an American statute, say that governs antitrust behavior by companies, or copyright protections, or liability for human-rights abuses. It must consider that world in interpreting the meaning of a treaty, to which the United States is a party but that may regulate conduct in countries very far away. And it must sometimes consider that world in determining the meaning of the U.S. constitution, which often seeks to balance individual liberties with the demands of national security.

Why...