Federal statutes do not come with instructions, but maybe they should. For as long as there have been statutes, lawyers and laymen have puzzled over their inevitable ambiguities. Gradually, case by case, courts have developed assorted tools of interpretation. Scholars, meanwhile, have conceived esoteric theories of how best to resolve statutory ambiguity. And the doctrine and the scholarship have become elaborate and sophisticated. But the very richness of this intellectual landscape has resulted in unpredictability and confusion. As theories and judges have multiplied, it has become ever more difficult to predict which judge will apply which theory to which case. And after centuries of judicial and scholarly effort, there is still no generally accepted theory of statutory interpretation. The central, unquestioned premise in this field is that the judiciary is the proper branch to design and implement tools of statutory interpretation. Scholars have unreflectively assumed as much, which is why, almost uniformly, they have implicitly aimed their work at the courts. This Article challenges that assumption. It asks whether Congress can and should help select the tools for interpreting federal statutes. The constitutional question turns out to be as important as the answer, because it adds a vital and neglected dimension to the debate about statutory interpretation. To ask whether Congress may codify a particular interpretive method is precisely to ask whether the Constitution requires the method that is to be displaced. This inquiry proves essential in locating statutory interpretation under the constitutional firmament. This Article concludes that Congress has constitutional power to codify some tools of statutory interpretation. Congress has used this power in the past, but only sporadically and unselfconsciously, at the periphery of the United States Code. The power itself is vast, however, and could transform the landscape of statutory interpretation. Because this power has received minimal systematic analysis, there is extraordinary potential for imprudent or unconstitutional overreaching. But used wisely, congressional power to legislate interpretive strategies may improve legislative-judicial communication and thus bring our legal system closer to its democratic ideal. This article therefore advocates codifying certain interpretive tools and techniques. And it suggests that the best form of codification would be as a set of federal rules: the Federal Rules of Statutory Interpretation.