This Article is about the nature and scope of legal argument. It considers the question of whether a court, when determining the precedential weight of one of its prior decisions, should consider historical evidence indicating that the decision was decided on the basis of improper motivations or as the result of political pressure. In a common law system in which courts pervasively rely on precedents as a source of law, that question is of obvious practical and theoretical importance. Yet courts and scholars have hardly even raised the question, let alone provided a satisfactory answer to it. Instead, they have assumed that such explanations are historical, not legal arguments—the kind of thing appropriate for law reviews, but not for courts of law.
This Article directly challenges that assumption. Drawing on a few rare examples when justices of the Supreme Court, or lawyers arguing before them, have sought to undermine court precedents by showing them to have been based on “extralegal” considerations, I argue that such efforts to historicize or—to use the term I prefer—impeach past decisions are a legitimate and potentially useful means of evaluating a decision’s precedential weight. Although various policy justifications may support excluding such arguments from judicial debate, I consider several such objections and explain why none is particularly persuasive. If the argument presented is sound, then not only should courts be more receptive to impeaching arguments, but—at least in the realm of constitutional law—both courts and scholars should perhaps broaden their understanding of how constitutional history bears on constitutional theory.