The overlapping jurisdiction of the United States and Peru in the Berenson case is a fundamental characteristic of modern international relations. In part it is the product of a legal principle related to the concept of a nation's sovereignty. As nations took shape, individuals and property (today that means—among other things—companies or corporations, ships, and aircraft) came to be identified for legal purposes with some sovereign, and this identification followed them wherever they went. This principle was then joined with an affirmation that the honor of a nation was injured when one of its citizens abroad or his or her property was subjected to an injustice. These two principles were interpreted to mean that each state would decide for itself when its citizens abroad had suffered mistreatment, how seriously the offenses had damaged the national honor, and what had to be done in order to make amends.
But these asserted rights had to be accommodated to the claim that nations exercised jurisdiction over everyone and everything within their boundaries. In effect, the individual or property abroad was placed in a legal relationship with two governments: one that claimed the individual as a citizen and one that insisted on the individual's compliance with its laws.
The awkwardness (or potential for trouble) of these overlapping claims was scarcely noted in the formative years of nation-states. Even in the relatively limited confines of the place of their birth (western Europe), nations tended to be isolated. Few people crossed their sovereign's borders. That being so, the father of international law, Hugo Grotius, the seventeenth-century statesman and jurist, made no explicit reference to how governments should ensure the protection of nationals traveling or residing abroad. Before the end of the eighteenth century, however, the Western world's commercial and industrial revolutions were opening a new era in international intercourse. By 1758, the year in which Emerich von Vattel's classic The Law of Nations was published, the treatment—or mistreatment—of foreign nationals had become a problem. From that point on, governmental agencies and law aimed at their protection developed rapidly.