The article cited seems to suggest that drug laws are only designed to prevent harms on the user, and that the only corresponding problem that flows from drug use is the black market. I think this is an oversimplification of the issue. Let me preface my argument by saying that I have no problem with the legalization of certain drugs such as marijuana but I am still unsure about more dangerous substances.
First, even if legalization of all drugs was successful in eliminating the black market for drugs, it is a stretch to make the assumption that this reduction would not be shifted at least in part - to other illegal activities. Sure, if after legalization, drug dealers filled their time helping old ladies across the street and went out and got real jobs, the crime rate would certainly go down. But this result assumes that the reason drug dealers sell black market goods is because their chosen profession has been made illegal by the government, not that they choose this profession specifically
because it involves goods on the black market. A strong argument exists, however, that drug dealers choose to engage in the black market because for lack of a better phrase where there is risk there is reward. They seek fast money and, with little to lose by getting caught, they view the benefit as exceeding the risk of imprisonment. If this scenario were true, drug dealers will simply switch to another high-risk high-reward activity such as armed robbery or running prostitution rings, and the legalization of drugs will simply shift many current drug dealers actions to different illegal activities.
Second, I agree that the only reason for regulating the use of recreational drugs would be harm, or threats of harm, caused by drug use. If drug use only harmed the user, then its regulation would have little justification. However, unlike mild drugs such as marijuana, in harming oneself many drugs (such as heroin, crack, methamphetamines, etc.) may incidentally have effects for others. For this reason, I believe that the idea that illegal drugs cause only self-harm is a myth. For example, the use of these drugs by a pregnant mother exposes the unborn child to toxic and permanently damaging substances. In fact, newborns of parents who use certain addictive substances (such as heroin or crack) often begin having withdrawals within minutes of birth. Children of parents who use serious drugs are harmed because they are subjected to the abuse of their drug-addicted parents. Drug use may also harm strangers who are on the receiving end of aggressive acts to which the impaired and overly aggressive drug users are prone. However, I dont have any information on the prevalence of these drug-related crimes or whether all such harms can be directly attributed to the existence of the black market.
Moreover, drug use harms family members by depriving them of the income of their addicted partners and parents. While it may be argued that legalization of all drugs would reduce this artificially inflated price that results from the black market, if drugs were taxed to raise revenue this may simply recreate the high-price conditions of the illegal black market. Conversely, if taxes were kept low to avoid this, then the price of drugs would be determined largely by their cost of production: a months supply of heroin might cost the same as a months supply of coffee or perhaps even of sugar. In this case, the basic principles of supply and demand suggest that consumption of these drugs which may very well be harmful to third persons will skyrocket.
For these drugs that impose harms on third parties, I believe that the government has at least some justification to continue laws against them. To the extent these drugs can be shown to have some beneficial health effects, I believe they should be allowed but limited in much the same way as current prescription medications. However, there is, as far as I know, no claim that any currently illegal drug other than marijuana has any health benefit for ordinary users.
As I am writing this, however, I find myself in a contradictory stance because many of my arguments for the continued laws against some illegal drugs would also be applicable to alcohol. I believe my argument rests, in part, on simply the extent of the harm that drugs such as meth, crack, and heroin have on their users compared to more mild drugs such as marijuana and alcohol.