Here is the problem. When a drug is approved by a health authority (and for convenience, we will use the US FDA, but the mechanics are similar in most western democracies), the FDA approves the drug for one or more indications at one or more dosage levels. But, the relationship between physicians and patient is confidential, so a doctor can prescribe any approved drug in any dosage chosen for any indication. But, should the patient sue the doctor, or should the licensing body investigate the doctor, if the drug was not prescribed at a dose and for an indication approved by the FDA, the doctor will be in the position of defending the use of the drug. A defense could be mounted by citing relevant scientific literature that shows that despite the lack of an approval, the drug has been shown to be safe and effective for the given indication.
So, if you are looking at the potential liability for the doctor, if it is a use as described by the FDA in its prescribing information, the FDA is on the hook for the liability. If not, the doctor is on the hook. Then there is the added problem that malpractice insurance may not cover liability for unapproved uses.
So, for a doctor, if you value your license and your house, you stick very close to the FDA prescribing information.
Government plans always try to look good on paper. The politicians will bark on about the tax revenue ignoring the fact that cannabis can be cultivated with little or no skill making it difficult, economically questionable, or impossible to collect the purported taxes.