Stanford Law Review
The question of whether courts should consult the laws of "other states" has produced intense controversy. But in some ways, this practice is entirely routine; within the United States, state courts regularly consult the decisions of other state courts in deciding on the common law, the interpretation of statutory law, and even the meaning of state constitutions. A formal argument in defense of such consultation stems from the Condorcet Jury Theorem, which says that under certain conditions, a widespread belief accepted by a number of independent actors, is highly likely to be correct. It follows that if a large majority of states make a certain decision based on a certain shared belief and the states are well motivated, there is good reason to believe that the decision is correct. For the Jury Theorem to apply, however, three conditions must be met: states must be making judgments based on private information; states must be relevantly similar; and states must be making decisions independently, rather than mimicking one another. An understanding of these conditions offers qualified support for the domestic practice of referring to the laws of other states, while also raising some questions about the Supreme Court's reference to the laws of other nations. It is possible, however, to set out the ingredients of an approach that high courts might follow, at least if we make certain assumptions about the legitimate sources of interpretation. Existing practice, at the domestic and international levels, suggests that many courts are now following an implicit Condorcetian logic.
Eric Posner & Cass R. Sunstein, "The Law of Other States," 59 Stanford Law Review 131 (2006).