With adults, paternalism is rational when it restricts freedom in order to prevent “far reaching, potentially dangerous, irreversible” harm, or secure a future good.
1. The adult does not know the risks/benefits
2. The adult knows, but has “weakness of will”
    (a) psychological or social pressure
    (b) irrational discounting of danger due to short vs. long term consequences

This approach can be used to justify Wilson's endorsement of the status quo (below).

Sasz 

Another utilitarian view; appeals to Mill's principle of maximum personal liberty that does not harm others.

Three major objections to current policies.

1. We are inconsistent in our treatment of very similar substances, particularly alcohol.
2. We routinely confuse cause and effect, confusing the bad effects of criminalizing behavior with the bad effects of the behavior, and confusing the symptom of a bad or unconventional life (excessive use of "self-medication") with the cause of a bad or unconventional life.
3. We impose a Puritan work ethic on everyone. But doing so is unjustified. It shows we do not really value individual liberty.

Wilson

Provides an extended discussion of benefits and costs, which makes it sound as if he's a utilitarian. Yet he counts drug addiction as a negative consequence without every saying why it is a negative consequence.

When he does compare the net benefits of free trade with the net benefits of our current policies, they seem more or less equal. So he summarizes this comparison of CONSEQUENCES with a choice: "support all unemployable addicts on welfare" in exchange for lower rates of crime, or accept our current high crime rates and spend the money on law enforcement instead of welfare.

What he does NOT emphasize --he confines it to a dozen words in the whole essay-- is that the crime we suffer from the current prohibition is often VIOLENT and RUTHLESS crime by the "criminal organizations seeking to control drug supplies." If we legalize narcotics and other "mind-altering drugs," we will sharply reduce the amount of violent crimes. 

[Editorial comment #1: Since Wilson prefers violent crime to paying for welfare, he seems to endorse the Puritan assumption discussed by Szasz: high murder rates are better than lazy people who don't work for a living.]

[Editorial comment #2: Wilson assumes that more access to drugs will mean that more people will become addicted, AND that we'll all pay to support these people. He does not discuss the fact that very few current addicts receive our financial support, even though he notes that we spend 500% more on law enforcement related to drugs than on "treatment." And he fails to confront Szasz's point that there's a limited pool of people willing to ruin their lives with alcohol and drugs -- most people have incentives to avoid excessive use of alcohol, despite its legality, and narcotics won't be any different.]

When he finally spells out his reasons why drug use is ITSELF a bad thing, he does not appear to be a utilitarian in any standard way. In fact, he is probably a Kantian, emphasizing the principle of respect for autonomy. HOW?

Narcotics are wrong because their use "alters one's soul." A narcotic high "debases" (i.e., degrades) the user. Nicotine (the drug in cigarettes) alters one's brain chemistry, but in a GOOD way. So Wilson appears to hold that self-medication is morally permitted when it ENHANCES our mental states and morally wrong when it temporarily REDUCES our mental functioning. (He also mentions our social nature, but that would seem to be an additional issue). So no matter what the other consequences, drug use is wrong whenever it is done to diminish our mental functioning. Nicotine, caffeine, etc., are morally allowable because they enhance our mental functioning.

SO WHAT IS WILSON'S MORAL STANDARD? He can be seen as extending Dworkin's position (above): It is right to paternalistically prevent drug use for the drug user's own good; using recreational narcotics puts us in a temporary state of diminished autonomy (if we're addicted, an ongoing state). If using recreational narcotics diminishes our natural ability to think and make good decisions, then prohibiting access to recreational narcotics preserves our autonomy, and our current drug laws are moral because they are a morally appropriate use of paternalism.

Shapiro

Examines assumptions about addiction. Click here.