I was fortunate to attend a conference in which the billions spent on one and two were demonstrated as to have had no effect whatsoever on the actual usage in the US which has continued to grow. These 'supply side' approaches are a dismal failure if one looks at the drugs present in the community and the access and use of drugs itself.
This "war on drugs" has however had an alternative purpose. While it has done nothing for drug abuse in US it has however armed considerable numbers of US police and security forces. These same armed forces are now being used for the 'war on terrorism'. If their success in the war on drugs is any measure of their overall success then terrorism shall likely rise. It strikes me as an outsider as veiled totalitarism.
Ironically, three, the arresting and punishing of drug users and drug dealers has resulted in more people jailed than at any time in the world in the once 'land of the free'. Dope smoking hippies are incarcerated with rapist and murderers and child rapists and child murderers. This continues today despite Alice's Restaurant and countless other attempts at moving the US legal system out of the dark ages. In Canada the situation is little better.
Clearly drug dealers should be distinguished from end stage users and if tobacco salesmen, ie pharmacies, grocers etc aren't going to be jailed then neither should marijuania smokers. A tobacco salesman, ie your local store is a more deeply evil and disturbed psychopathic member of society than your average sick marijunia or tobacco smoker.
The businessmen who pander to depravity and profit from sickness are at least lower on the evolutionary ladder. Regulation is indicated if only to keep these predators in check.
In this regard that's what 'decriminalization' means.
Finally, treating alcoholics and addicts rather than punishing them, recognising that alcoholics and drug addicts are sick people not bad or evil people is the most successful approach to date to the drug and alcohol abuse problems.
The trouble with legalization is simply that the more drugs or alcohol available the greater the per centage of abuse. Let's for argument say 10 % of the population will abuse alcohol. Say other 10% will abuse coke and another 10% marijuania. Despite the overlap that actually occurs the overall percentage of the population with abuse problems rises with availability. Hence the benefits of laws that restrict usage.
When I was in Amsterdam a few years back I was shocked that I couldn't find anywhere to sit without there being drugs evident. I like eating in smoke free restaurants. I like coffeeshops where there's no marijuania. The majority of people, from my point of view, are like me. I like quiet too. If drinking and drugging was allowed in libraries, for instance, it wouldn't be the drunks and drug addicts who'd want quiet. I want the police to maintain the ability to pick up people who are 'drunken and disorderly'.
Diversion is a marvellous coupling of the legal and medical model and it works amazingly well. This is where people caught abusing drugs or alcohol are 'diverted' to treatment models of care (the medical model) and "recovery" versus the traditional 'punishment' jail model. Alcoholics who lose their licenses for driving are required to attend AA meetings and despite the external force have a significant success staying off alcohol.
Note that this is not 'legalization'. Marijuania smokers and drug addicts like James Bond want a "license" to use. Personally I understand why society has restrictions and accept that drugs of abuse should have restrictions. This is for the benefit of individuals at risk and society at large. It doesn't refer to traffickers. Frankly I would simply fine traffickers out of business. I don't want to have taxes pay for them in jail. In fact the drug dealers I knew were quite happy with the status quo because their profits were greatest now. Indeed it almost seemed like they were in league with the legislators.
As for treatment, it's highly effective. Alcoholism and addiction are medical diseases which can be prevented and identified early enough to avoid the harm that abuse causes. There are effective treatments and a whole array of methods are available to help people to change their behaviours. The earlier one intervenes the greater the success.
I grow weary with those proponents who casually say it's a 'choice' because the evidence is that the brain is changed by addiction. Further I've seen a man with Gaucher's disease (vascular allergy to tobacco) lose all his fingers and toes before he could stop smoking. He didn't "want" toand he would choose to not if he was privileged as those who are quick to deny him medical services.
So many of the major medical illnesses of today are recognised as 'diseases of lifestyle' including many heart diseases and lung diseases and cancers. So if addiction is 'choice' so are they. We don't jail obese people but instead we have a variety of treatments and we do give them new hip replacements when they exceed their load tolerance.
So yes, decriminalize but legalization should probably wait till we've treated the last of the asthmas and lung cancers from the 'legalized' tobacco.