The Supreme Court, in a line of several cases over the past decade, has established a rigorous federal constitutional excessiveness review for punitive damages awards based on the Due Process Clause. As a matter of substantive due process, says the Court, punitive awards must be evaluated by three “guideposts” set forth in BMW of North America v. Gore: the degree of reprehensibility of the defendant's conduct, the ratio between punitive and compensatory damages, and a comparison of the amount of punitive damages to any “civil or criminal penalties that could be imposed for comparable misconduct.” Following up on this pronouncement in State Farm Mutual Automobile Insurance Company v. Campbell the Court indicated that “few awards exceeding a single-digit ratio between punitive and compensatory damages, to a significant degree, will satisfy due process.” Unfortunately, neither the “guideposts” nor the single-digit multiple rule have any basis in the law of due process and represent nothing more than the imposition of the Court’s own standards for punishment in place of those of the states. This Article reveals the defectiveness of this jurisprudence by exposing the absence of precedential foundation for the Court’s current view. More significantly, this Article demonstrates that the Court’s interpretation of the Due Process Clause is at odds with important rules of constitutional construction, mainly those supplied by the Ninth and Tenth Amendments, which protect unenumerated rights and limit the national government to exercising delegated powers, respectively. Together, these amendments prohibit expansive interpretations of the Constitution that disparage rights retained by the people and that arrogate to the national government powers that neither the states nor the people ever relinquished. The Court’s interpretation of the Due Process Clause with respect to punitive damages transgresses both of these limitations. This Article suggests that a proper understanding of due process reveals that it requires only that punitive awards be reserved for wrongdoing beyond simple negligence, that jurors be instructed that any punitive award they impose must be designed to further states’ legitimate interest in punishment of in-state conduct and deterrence, and that judicial review of the awards be available to check adherence to these requirements. Beyond that, the Due Process Clause fails to require that punitive damages awards be constrained to a particular level.