The mistake made in USA in 1933 was to end prohibition of alcohol under the Volstead Act, but to leave in existence prohibition of cocaine and heroin under the Harrison Tax Act.

This grievous error was then compounded in 1937 with the Marihuana Tax Act, and by the various Acts that replaced them in USA and elsewhere after WWII.

What do I mean by 'Prohibition'?

I take it to be the wording of Article 2.5.b. of the Single Convention on Narcotic Drugs 1961 of the United Nations:
    ... prohibit the production, manufacture, export and import of, trade in, possession or use of any such drug ...
however expressed in the various prohibitory Acts.

Why is it not all right to grade drugs so that the more 'dangerous' drugs may remain 'prohibited' while less dangerous (or more beneficial) drugs are released from 'prohibition'?

Because individual drugs, or their use or abuse by individuals, are not as dangerous as is 'prohibition' itself. 'Prohibition' automatically makes a substance more dangerous, and spreads its use and its abuse. In particular, 'prohibition' spreads the use and abuse of a substance to our children, the very people we particularly hope to defend.

The mechanism of 'prohibition' of a substance

1. No substance has been 'prohibited' unless it is already desired and in use by a portion of the population. This is an almost certain prerequisite for 'prohibition'.
2. We ought not expect our law enforcement officers to select which laws they should enforce rigorously and which they should ignore. Such a culture brings laws in general into disrepute.
3. Transport price factor:

• When a substance is first 'prohibited', some of the users travel to where the substance is still available, and procure as much as they consider they may bring back in optimum safety. They sell the quantity surplus to their immediate needs in order to recoup their costs. The cost of the substance has now been increased by a 'transport factor'.

4. Risk price factor:

• Some of these importers are caught and punished, and this again increases the cost by a 'risk factor'.

5. Pyramid selling:

• Because all phases of wholesaling and retailing are illegal, a pyramid system of distribution is forced on the distributors and users. This system reduces to a minimum risk of discovery by connection, and risk of liability for the misfortunes of others in the pyramid.
• Each person in a layer above the bottom of the pyramid is responsible for recruiting sufficient buyers to maintain viability, and whether greed or funding own use is the motive, the impressionable or disaffected young are obvious targets. The system provides a previously unimaginable income for the young.
• Pyramid sales makes replacement of persons who withdraw for whatever reason very easy. Each replacement recruits new users.

6. Concentration of substance

• Concentration of the substance reduces the risks of handling, but increases the risks of using. Hence the perpetual tendency towards higher concentration of substance. Hence the increasing use of injection or smoking as a means of use, and the decreasing safety margins for users

7. Organised Crime

• At some stage in the above processes it becomes worth the while of organised crime to insert itself into the processes of production, transport and distribution. Turf wars start.

8. Administrative Corruption

• By now there are criminal risks in growing, manufacture, transport, border crossings and distribution, so the search is on for corruptible inspectors, customs personnel, police, etc, and inevitably some are found, and systemic corruption develops. The corruption factor is added to the price.

9. Increasing incarceration and prosecution rates

• 'Prohibition' has been the principle engine of growth in the USA prison industry and has started to send other countries in the same direction. The USA is now incarcerating at about 7 times the rate of other countries.
• There has been comparable growth in the 'courts industry' responsible for sending people to prison.

10. Civil rights erosion

• 'Prohibition' has also reduced the civil rights of the people through mechanisms such as 'deeming' provisions for trafficking.

11. Political corruption

• By 1997, some 45 years of international 'prohibition' of illicit drugs had raised the illicit drug industry to number 2 in world trade ranking by value, after arms. The inherent costs of producing armaments are immense. A warship costs far more per water line length than a commercial vessel. A military vehicle costs far more than a comparable civilian vehicle. The costs of producing illicit drugs without the transport, risk and corruption factors are comparable with the costs of producing aspirin or tomatoes. The 'surplus' available to the illicit drug industry is first in the world ranking, is dependent on retaining 'prohibition', and has the surplus for corrupting the political process necessary for its survival. This adds a political corruption factor.

12. Economic corruption

• The banking and gambling industries are essential for the laundering of the illicit proceeds of illicit drugs and for their transfer between countries.
• Production of the illicit drugs used by the first world has destroyed the economies and normal life of such countries as Colombia, Mexico, Peru, Ecuador, Afghanistan, Burma and others.
• 'Prohibition' is the most effective way of increasing the danger, spreading the use, corrupting government, endangering children yet dreamt up by our inventive species.
• 'Prohibition' is far, far more dangerous than any of the substances that have yet, or could in the future be 'prohibited'.

We must beware the temptation to consider that it is all right to retain 'prohibition' for some drugs, because they are considered more dangerous, but decriminalised others because they are considered less dangerous. To do so perpetuates the grevious errors identified above.  It is 'prohibition' that is the danger.

We must be aware, particularly in this US Presidential election year, that it is the party machines that get corrupted, where only candidates favourable to 'prohibition' will be selected. Only the drug warriors will attract sufficient campaign funds to stand a hope of election.