Oregon legalized assisted suicide when voters approved a ballot measure enacting the Oregon Death With Dignity Act (ODWDA). ODWDA exempts from civil or criminal liability state-licensed physicians who, in compliance with the specific safeguards in ODWDA, dispense or prescribe a lethal dose of drugs upon the request of a terminally ill patient. The drugs physicians prescribe under ODWDA are regulated under a federal statute, the Controlled Substances Act (CSA or Act). An Interpretive Rule issued by the Attorney General (Gonzales (D)) addressed the implementation and enforcement of the CSA with respect to ODWDA. It determines that using controlled substances to assist suicide is not a legitimate medical practice and that dispensing or prescribing them for this purpose is unlawful under the CSA. The CSA explicitly contemplates a role for the States in regulating controlled substances. Its preemption provision provides: “No provision of this subchapter shall be construed as indicating an intent on the part of the Congress to occupy the field in which that provision operates . . . to the exclusion of any State law on the same subject matter which would otherwise be within the authority of the State, unless there is a positive conflict between that provision . . . and that State law so that the two cannot consistently stand together.” §903. Under ODWDA, there must be a diagnosis from their attending physician that a patient has an incurable and irreversible disease that, within reasonable medical judgment, will cause death within six months. The physician must also determine whether a patient has made a voluntary request, ensure a patient’s choice is informed, and refer patients to counseling if they might be suffering from a psychological disorder or depression causing impaired judgment. A second “consulting” physician must examine the patient and the medical record and confirm the attending physician’s conclusions. Oregon physicians may dispense or issue a prescription for the requested drug, but may not administer it. The physicians must keep detailed medical records of the process leading to the final prescription, which Oregon’s Department of Human Services reviews, §127.865. Physicians who dispense medication pursuant to ODWDA must also be registered with both the State’s Board of Medical Examiners and the federal Drug Enforcement Administration (DEA). On November 9, 2001, without consulting Oregon or apparently, anyone outside his Department, the Attorney General, John Ashcroft, issued an Interpretive Rule announcing his intent to restrict the use of controlled substances for physician-assisted suicide. The Attorney General ruled “assisting suicide is not a ‘legitimate medical purpose’ within the meaning of 21 CFR 1306.04 (2001), and that prescribing, dispensing, or administering federally controlled substances to assist suicide violates the Controlled Substances Act. The State of Oregon (P), joined by a physician, a pharmacist, and some terminally ill patients, all from Oregon, challenged the Interpretive Rule in federal court. The United States District Court for the District of Oregon entered a permanent injunction against the Interpretive Rule’s enforcement. A divided panel of the Court of Appeals for the Ninth Circuit held the Interpretive Rule invalid. The Interpretive Rule altered the “ ‘ “usual constitutional balance between the States and the Federal Government” ’ ” without the requisite clear statement that the CSA authorized such action. The Supreme Court granted certiorari.