Drug policy reform is an issue unlike any other, riddled with enormous stereotypes regarding the rhetorical integrity of the other sides, and more malice and opportunism than that which mars other equally contentious issues. What you may discover, however, is that at its core, the attitudes that have been adopted (or should I say, enforced) worldwide with regards to law's role in changing patterns of drug use are entirely misguided.
The first misguided conception, and beyond a doubt the most important, is the perception that decreases in drug use will result from its prohibition. This stems from the extremely simple view that prohibition of an act has a direct correlation with the same act's cessation, which you'll find grows increasingly false with the desire of an individual to engage in such an act. This is essentially self-explanatory. Government doesn't exist as an absolute figure that mandates morality by rule of law, rather it exists solely as an influence (however overwhelming) that implies consequences for disobedience of its verdicts. Thus, the ridicule with which drug users treat drug policy, in combination with the the social "taboo" associated with drug use and the relatively minor consequences for drug use, essentially eliminate any significant chance of reduced drug use. This is why, following legalization in the Netherlands, for instance, we noticed no significant change in drug use, or at times even a reduction.
This is not to imply, however, that harsher penalties will eliminate drug use. Countries such as Malaysia that have taken radical steps to eliminate drug use, going so far as to institute the death penalty for those implicated in drug possession, have created an entirely new class of people, who face such severe penalties for their actions that there no longer remain any consequences for any further action they take. This is especially true of players in the largest of drug cartels - those who are quick to fill the insatiable demand for intoxication are immediately castigated by the government as criminals and low-lives (as opposed to all other opportunist businessmen), and facing no further consequences for any of their actions considering the already severe punishments looming over their lives, they are essentially free to conduct themselves as criminals.
Now, let's take a look at another possible situation, or, more accurately, the situation that existed prior to the popular notion that drugs could be successfully prohibited: that of intoxicating substances being widely available by commercial means and, most importantly, regulated. As drug law stands, there's absolutely no control over what's sold - as a result of this, a heroin user on the street may have to deal with extremely dangerous phenomena such as the variance in purity between drug sales. This has immediate and obvious consequences. After a significant tolerance has been accumulated by a heroin user, for instance, the permanence of the tolerance is hardly predictable, and so the combination of an unexpected decrease in tolerance and an unexpected increase in drug purity is immediately dangerous, if not fatal. This is to not even touch upon the fact that drugs are often laced or cut with substances that are intrinsically more harmful than the drugs themselves - something which is ironically cited as a justification for continued prohibition by many of those in charge of drug policy. Similarly problematic is the fact that the cost of drugs skyrockets with the increased cost of production and transportation that occurs as a direct result of prohibition, which in turn creates much more crime, resulting from the enormous strain drug use now places on the individual's budget. As a result, everybody is now subject to victimization.
Now we come to the third, and perhaps most troubling issue in drug policy: the idea that it's the government's responsibility to actually prevent its constituents from using drugs. This calls into question serious issues as to the nature of government, particularly with regards to whether or not government should be permitted to legislate regarding consensual actions. This is, naturally, little more than a question of opinion, to which my own answer is a resounding "no." William Buckley noted that the consequences of drug use do spread beyond that which affects the individual, but this is irrelevant in a prohibitionist's argument, in the face of the fact that prohibitionist drug policy exacerbates the negative consequences of drug use and has little significant effect on the actual rates of usage.
The fourth serious problem is the nature of invasiveness that drug policy permits, whether in a legislative sense, as per the deprivation of freedom and property, or in a more direct sense, as per the deprivation of privacy, is the power of government over its citizens. All of these occur with any increased governmental power, which is hardly a point of debate. What's more troubling in this issue is the semantic trickery by which the government is capable of deploying these tactics. By creating what's essentially a sub-class of drug users and drug sellers, the government is able to imply that the consequences for drug use and distribution are less serious due to the faults they impose upon these citizens. As a direct result of this, we see legislation allowing such insane things as asset forfeiture, wherein a citizen can be deprived of their property without any semblance of due process - in the United States, for example, the citizen is essentially granted the burden of proof, being forced to demonstrate that their property hasn't even been involved in any drug-related transactions, which flies in the face of nearly everything the country was founded upon. Similarly, the fourth amendment of the United States' Constitution, pertaining to the permissibility of search and seizure of private citizens and their belongings, has been nearly destroyed in the face of increasingly questionable tactics - drug dogs, for instance, despite failure rates of nearly 15% as per detecting traces of drugs, are treated as "probable cause" to search a vehicle in the event that they alert the police to perceived traces of illegal drugs. Police have attempted to monitor electric bills and detect heat signatures using infrared equipment in order to discover people growing pot within their houses - quite contrary to the doctrine of "plain view" which previously search and seizure or, at the very least, led to the procurement of a search warrant. It's clear that the government will take any available steps in the enforcement of its laws - the question in this case, however, is not whether or not these tactics are appropriate, rather, it's whether or not the goals they're attempting to achieve are achievable at all. The answer to both questions, in my opinion, is again "no." They have overstepped far too many boundaries as it stands, and made little progress towards any of their stated goals, leaving a legacy of this policy as pointless and short-sighted as the policy of prohibition, the only significant difference being that alcohol was popular enough to garner enough resistance for prohibition to end.
Politicians, at the root of their motivations, are attempting to be elected, and will take hold of any issue that arises, in the context of their own morality (the integrity of which I'll leave to speculation), in order to ensure their further election. There are exceptions to this generalization, of course, but nonetheless, more radical politicians are coerced into agreeing with the majority, in spite of good sense, to ensure their own success, and in the wave of popular support for drug prohibition, they are rendered powerless against it. Drug use was originally prohibited as an extension of racial scapegoating, and the historical roots of this are so troublesome that they need little further elaboration - although let it be said that arrest rates for drug use currently are much more heavily weighted towards minorities than figures for drug use itself.
I'll leave you with one of the most bothersome things I've witnessed in the context of the "drug war," a DEA-sponsored exhibit that attempts to link the attacks of 9/11 to drug use. Now, when I said "opportunism" at the beginning of this writeup, I meant it. This is among the most deplorable of political tricks, and one that should serve as a reminder that the government's justification for its actions may fly in the face of reason, any notion of decency or even its own investigations:
"there is no reliable evidence that Bin Ladin was involved in or made his money through drug trafficking"
— 911 Commission Report, page 171
Yikes.