For generations in Western culture, legal jurisdiction over people and events within a nation's borders rested only with that nation's government. In recent years, however, human rights activists have pushed the concept of "universal jurisdiction," by which judges in one country can assert authority to prosecute any offense regardless of where it took place. The zealots have found their champion in one Baltasar Garzon, a judge on the Spanish National Court. A socialist activist as a college student, Garzon at age 32 became the youngest magistrate on the court. Now 53, he has spent many of the intervening years practicing...