SCOTUS Hearing Assisted Suicide Act

From what I've been reading it looks like the division in the court really appears to split on who has the final say on what is the proper use of a drug. Does the DEA determine the valid uses or is it up to the state who regulates medicine locally? And does the Attorney General have the authority to stop doctors from applying state approved uses of drugs?

This one is very difficult. There are valid arguments either way.
The Controlled Substances Act per the DEA:

The CSA places all substances that are regulated under existing federal law into one of five schedules. This placement is based upon the substance's medicinal value, harmfulness, and potential for abuse or addiction. Schedule I is reserved for the most dangerous drugs that have no recognized medical use, while ScheduleV is the classification used for the least dangerous drugs. The act also provides a mechanism for substances to be controlled, added to a schedule, decontrolled, removed from control, rescheduled, or transferred from one schedule to another.

Proceedings to add, delete, or change the schedule of a drug or other substance may be initiated by the Drug Enforcement Administration (DEA), the Department of Health and Human Services (HHS), or by petition from any interested party, including the manufacturer of a drug, a medical society or association, a pharmacy association, a public interest group concerned with drug abuse, a state or local government agency, or an individual citizen. When a petition is received by the DEA, the agency begins its own investigation of the drug.

The DEA also may begin an investigation of a drug at any time based upon information received from law enforcement laboratories, state and local law enforcement and regulatory agencies, or other sources of information.

Once the DEA has collected the necessary data, the DEA Administrator, by authority of the Attorney General, requests from the HHS a scientific and medical evaluation and recommendation as to whether the drug or other substance should be controlled or removed from control. This request is sent to the Assistant Secretary of Health of the HHS. Then, the HHS solicits information from the Commissioner of the Food and Drug Administration and evaluations and recommendations from the National Institute on Drug Abuse, and on occasion, from the scientific and medical community at large. The Assistant Secretary, by authority of the Secretary, compiles the information and transmits back to the DEA a medical and scientific evaluation regarding the drug or other substance, a recommendation as to whether the drug should be controlled, and in what schedule it should be placed.

The medical and scientific evaluations are binding to the DEA with respect to scientific and medical matters. The recommendation on scheduling is binding only to the extent that if HHS recommends that the substance not be controlled, the DEA may not control the substance.

The question really comes down to, is use of a controlled drug for assisted suicide an invalid use. That isn't addressed here. Most drugs used in assisted suicide have other legitimate uses. From what I see, the state defines legitimate uses as well.

Lastly, is the Attorney General qualified to determine what is a legitimate use? I think not.

Maybe the end topic is more complex. Though it really shouldn't be.