What do the contemporary issues of military tribunals, same-sex marriage, informational privacy, and reproductive rights have in common? All of them raise constitutional issues that fall under the umbrella of the Due Process Clauses of the United States Constitution. Th e resolution of all of them hinges, to a dramatic degree, upon ever-evolving judicial interpretations of that “due process of law” mandate. Few Americans understand the common constitutional source of these rights, its ancient history, or the ornate set of rights that today fall within the due process embrace. Even many scholarly debates about judicial activism and the need to return to “original meaning” of constitutional rights—especially original meaning of due process of law—fail to apprehend the full due process terrain. Instead they oft en cherry-pick issues within the doctrine to criticize or praise specifi c pieces of the law, and are unmindful of the implications of these critiques for other rights that fl ow from the same due process artery. In particular, many critics who insist that the phrase due process historically and logically embraces only procedural, not substantive rights, ignore the multiple ways in which procedural rights fl ow from substantive rights and depend upon them. More fundamentally, the arguments against substantive due process rights simply blink too much doctrinal reality: Americans’ settled expectations of ordered liberty and baseline sense of what constitutes a legitimate exercise of government power now include a complex set of procedural and substantive rights that emerged since the late 1800s under the due process framework.