Thank you very much for asking this question. This is a very intelligent question. It is also a very helpful question for us because it helps illuminate the limitations of the word legal, and the importance of the kinds of regulations that a legal regime uses. It is also an important question because it puts into focus some of the issues of demand, legitimate use, medical use, self-medication, and non-medical use.

Drugs that can be used pursuant to a doctor's prescription are legal in a very narrow sense. The user of the drugs has obtained the drugs directly from the doctor or from a pharmacy pursuant to a prescription written by the doctor with whom the patient has a professional relationship. The drugs are obtained after a bona fide examination and consultation in which the doctor has examined the patient and reviewed the history and made a good faith determination that the medication is the appropriate medication for the patient's condition. The prescription is for a dosage consistent with the medical community's accepted practices, and all the components of the transactions comply with DEA's regulations for practitioners.

Depending on a variety of circumstances, this narrow legal zone is inconvenient, medically preposterous, offensive to individual liberty, impractical or otherwise unrealistic, and thus widely disregarded leading to a criminal market. When a legal scheme deviates substantially from what the affected public considers realistic, the scheme gets violated. A classic example is highway speed limits. A six lane boulevard, divided by a median, might have a posted speed limit of 25 mph, highly desired by the people whose homes are directly on that street. Yet most drivers are likely to drive 35 or 40 on such a road if traffic permits. On an interstate highway, a posted speed limit of 55 is likely to be exceeded. Most drivers accept the need for speed limits in the abstract, but drive in technical violation of those limits.

Prescription drugs are expensive. A prescription for powerful pain medication after a procedure may often be for more doses than the patient needs to use before the pain subsides. The patient is reluctant to throw the expensive extra doses away. At a minimum, six months later when a family member is in pain, the patient may give their medication to a relative who is not named on the prescription label -- a violation of the law. In a society in which many households' surplus goods are sold on Ebay, the culture accepts selling what you don't need. Someone might feel that it is thrifty and good sense not to waste and throw away surplus drugs but to sell them to someone who needs them. The seller may desire to make the drugs available to a person who has a bona fide need for the drugs, but who, for any number of reasons, cannot get a prescription for that medication filled. Those reasons could include lack of health insurance, lack of a job, or illegal status in the United States. The seller may have no knowledge of nor intent to support an addict's habit. The prescription system can be inconvenient and economically wasteful.

In some circumstances the potential risks to the patient of using the drugs are very small. The patient may have had a prescription, but is required to see a doctor every 30 or 60 days in order to get a new prescription. The patient may reasonably believe that these doctor visits are medically unnecessary, but provide the doctor with income, even if they are necessary to comply with regulations designed to prevent abuse. The patient may reasonably decide that their use is not abusive, and that the law is overbroad as applied to them, and should be ignored.

In many circumstances, patients know enough about their medical condition and the medications and their effects and side effects that they consider the doctor's participation in obtaining the medication to be medically superfluous, expensive, inconvenient, and an interference in their liberty.

In other cases, persons are addicted to opiate medications. Their addiction can be satisfied by heroin, or by legal narcotics. But doctors know that if they provide narcotics to addicts they risk being prosecuted. So addicts do not have legal access to legal narcotics.

The idea that these are legal drugs, for the most heavy users of these drugs, is absurd. No doctor feels it is legal for them to prescribe to such persons, and no drug user who is an addict has legal access to the legal drugs.

The legal narcotics may be much more desirable for the addict than heroin because they are made in pharmaceutical factories and are pure -- that is they are free of any dangerous contamination or cut, unlike street heroin -- and they are of a known dosage. No need to worry that it is weak and you a getting ripped off, or that you will be poisoned. Legal opioid medications are highly desirable substitutes for illegal heroin. If heroin were legal, the market in the legal prescription pharmaceuticals would go down.

The illegal market of legal prescription drugs is natural because our law does not consider maintenance of addiction a legitimate medical circumstance. When it is not a crime to be an addict, and addicts can legally get the drugs they need, the illegal secondary market in pharmaceutical products will be substantially reduced. Addicts will stop robbing and burglarizing pharmacies to get drugs, and the street market in stolen or fraudulently obtained drugs will be substantially be reduced.

For the drug users who are most problematic and already involved in the illegal drug market, the illegal market in prescription drugs, makes sense, but in no way is it for them a legal market in drugs.