Hi folks, rjeffb here. I am a regulatory compliance specialist. I don’t speculate about regulations, I go read them so I know the facts.
There is no DEA regulation requiring, nor even authorizing DEA to require, a drug screen in order for a state and DEA licensed physician to prescribe or refill a controlled substance. Just Google “21 CFR 1306” and see for yourself.
A physician is indeed charged with making reasonable assurances that drugs prescribed are not being diverted, and he (and the pharmacist as well - that is contained explicitly in the regulation) can be held both civilly and criminally responsible if they do not take reasonable measures to confirm the medical need, including (this is actually out of a different DEA regulation dealing with on-line pharmacies) a personal, physical examination. But what the method of that examination should be is left to the practitioner (as it would have to be under the 10th amendment to the Constitution). Note that I am not an expert in the controlled substance laws and Board of Medicine/Board of Pharmacy regulations for all the states - although I do know quite a few - so it is not impossible that this could be a state requirement. But it is absolutely untrue that DEA requires drug screening tests before a doctor can prescribe or renew a controlled substance.
By the way, a piece of possibly pertinent information. A whole slew of Schedule III narcotics are about to be rescheduled as Schedule II, including several that were mentioned in this thread (go to fda.gov and do a search for “schedule III reclassification”). This has DEA breathing down the necks of all licensees who have Schedule IIIs that are about to become Schedule II due to the tremendously more explicit and challenging security requirements (example: we have to have documented evidence proving that our safe can undergo an attack by an X-Ray machine without revealing enough about its internal mechanism to help a safecracker open it…“Mission Impossible” stuff). Everybody is very nervous about having their DEA license revoked, or simply not being authorized to issue DEA 222s (request for Schedule II/Schedule III orders), which DEA can do without a hearing.