Some people think that the practices of many courts in many countries, or in many relevant countries, offer helpful guidance to courts in other countries, when those courts are approaching hard or novel questions. In their view, the practices of many courts create a body of law in which other courts should be highly interested. The obvious question is: Why?

In The Law of Other States, we attempt to make progress on this question. Our focus was not principally on the use of foreign precedents in the constitutional rulings of the U.S. Supreme Court. We meant to take that controversial and specialized problem as part of a much more general one, which involves courts in one jurisdiction using the decisions of courts in other jurisdictions. Within the United States, state courts frequently refer to the decisions of other state courts, even when construing state constitutions. The high courts of many nations refer to the decisions of high courts of other nations. The problem is that it is not self-evident that the practices of courts AY should be taken as valuable or informative for court Z. Exploration of that problem might also illuminate the question of whether and when a legislator or administrator in one state should attend to the decisions of legislators or administrators in other states.