This is an open access title available under the terms of a CC BY-NC-ND 4.0 International license. It is free to read at Oxford Academic and offered as a free PDF download from OUP and selected open access locations. An authoritative and first-of-its-kind critical constitutional history of the war on drugs that shows how drug prohibition was shaped by constitutional law, and how constitutional law was shaped by drug prohibition. The U.S. government's decades-long "war on drugs" is increasingly recognized as a moral travesty as well as a policy failure. The criminalization of substances such as marijuana and magic mushrooms offends core tenets of liberalism, from the right to self-rule to protection of privacy to freedom of religion. It contributes to mass incarceration and racial subordination. And it costs billions of dollars per year--all without advancing public health. Yet, in hundreds upon hundreds of cases, courts have allowed the war to proceed virtually unchecked. How could a set of policies so draconian, destructive, and discriminatory escape constitutional curtailment? In The Constitution of the War on Drugs, David Pozen provides an authoritative, critical constitutional history of the drug war, casting new light on both drug prohibition and U.S. constitutional development. Throughout the 1960s and 1970s, advocates argued that criminal drug bans violate the Constitution's guarantees of due process, equal protection, federalism, free speech, free exercise of religion, and humane punishment. Many scholars and jurists agreed. Pozen demonstrates the plausibility of a constitutional path not taken, one that would have led to a more compassionate approach to drug control. Rather than restrain the drug war, the Constitution helped to legitimate and entrench it. Pozen shows how a profoundly illiberal and paternalistic policy regime was assimilated into, and came to shape, an ostensibly liberal and pluralistic constitutional order. Placing the U.S. jurisprudence in comparative context, The Constitution of the War on Drugs offers a comprehensive review of drug-rights decisions along with a roadmap to constitutional reform options available today.