Next Thursday I am scheduled to debate Robert White, co-author (with Bill Bennett) of Going to Pot: Why the Rush to Legalize Marijuana Is Harming America, on Glenn Beck's radio show. Each of us will get half an hour or so to make his case before taking questions from Beck and each other. Here is what I plan to say:

Marijuana Prohibition Is Unscientific

A few days before the House of Representatives passed a federal ban on marijuana in June 1937, the Republican minority leader, Bertrand Snell of New York, confessed, "I do not know anything about the bill." The Democratic majority leader, Sam Rayburn of Texas, educated him. "It has something to do with something that is called marihuana," Rayburn said. "I believe it is a narcotic of some kind.

That exchange gives you a sense of how much thought Congress gave marijuana prohibition before approving it. Legislators who had heard of the plant knew it as the "killer weed" described by Federal Bureau of Narcotics Commissioner Harry Anslinger, who claimed marijuana turned people into homicidal maniacs and called it "the most violence-causing drug in the history of mankind." Anslinger warned that "marihuana causes white women to seek sexual relations with Negroes" and estimated that half the violent crimes in areas occupied by "Mexicans, Greeks, Turks, Filipinos, Spaniards, Latin Americans, and Negroes may be traced to the use of marihuana."

Given this background, no one should pretend that marijuana prohibition was carefully considered or that it was driven by science, as opposed to ignorance and blind prejudice. It is hard to rationally explain why Congress, less than four years after Americans had emphatically rejected alcohol prohibition, thought it was a good idea to ban a recreational intoxicant that is considerably less dangerous.

It is relatively easy, for example, to die from acute alcohol poisoning, since the ratio of the lethal dose to the dose that gives you a nice buzz is about 10 to 1. According to the U.S. Centers for Disease Control and Prevention (CDC), about 2,200 Americans die from alcohol overdoses each year. By contrast, there has never been a documented human death from a marijuana overdose. Based on extrapolations from animal studies, the ratio of the drug's lethal dose to its effective dose is something like 40,000 to 1.

There is also a big difference between marijuana and alcohol when it comes to the long-term effects of excessive consumption. Alcoholics suffer gross organ damage of a kind that is not seen even in the heaviest pot smokers, affecting the liver, brain, pancreas, kidneys, and stomach. The CDC attributes more than 38,000 deaths a year to three dozen chronic conditions caused or aggravated by alcohol abuse.

Another 12,500 alcohol-related deaths in the CDC's tally occur in traffic accidents, and marijuana also has an advantage on that score. Although laboratory studies indicate that marijuana can impair driving ability, its effects are not nearly as dramatic as alcohol's. In fact, marijuana's impact on traffic safety is so subtle that it is difficult to measure in the real world.

Last February the National Highway Traffic Safety Administration (NHTSA) released the results of "the first large-scale [crash risk] study in the United States to include drugs other than alcohol," which it described as "the most precisely controlled study of its kind yet conducted." The researchers found that once the data were adjusted for confounding variables, cannabis consumption was not associated with an increased probability of getting into an accident.

That does not mean stoned drivers never cause accidents. One challenge in assessing the extent of the problem is that many of the drivers who test positive for marijuana are not actually impaired, since traces of the drug can be detected long after its effects wear off. That means marijuana-impaired drivers get mixed in with drivers who happen to be cannabis consumers but are not under the influence while on the road, which would tend to mask the drug's role in crashes. Still, alcohol is clearly a much bigger factor in traffic fatalities.

Last year, during a congressional hearing on the threat posed by stoned drivers, a NHTSA official was asked how many traffic fatalities are caused by marijuana each year. "That's difficult to say," replied Jeff Michael, NHTSA's associate administrator for research and program development. "We don't have a precise estimate." The most he was willing to affirm was that the number is "probably not" zero.

The likelihood of addiction is another way that marijuana looks less dangerous than alcohol. Based on data from the National Comorbidity Survey, about 15 percent of drinkers qualify as "dependent" at some point in their lives, compared to 9 percent of cannabis consumers. That difference may be especially significant given the link between heavy alcohol consumption and premature death.

All told, the CDC estimates that alcohol causes 88,000 deaths a year in the United States. It has no equivalent estimate for marijuana. We may reasonably assume, along with Jeff Michael, that marijuana's death toll is more than zero, if only because people under the influence of cannabis occasionally have fatal accidents. But the lack of a definitive answer highlights marijuana's relative safety, which points to a potentially important benefit of repealing prohibition: To the extent that more pot smoking is accompanied by less drinking, an increase in cannabis consumption could lead to a net reduction in drug-related disease and death.

The comparison of alcohol and marijuana presents an obvious challenge to anyone who thinks the government bans drugs because they are unacceptably dangerous. If anything, that rationale suggests marijuana should be legal while alcohol should be banned, rather than the reverse. Judging from this example, the distinctions drawn by our drug laws have little, if anything, to do with what science tells us about the relative hazards of different intoxicants.

Marijuana Prohibition Is Unconstitutional

When dry activists sought to ban alcoholic beverages, they went through the arduous process of changing the Constitution, which prior to the ratification of the 18th amendment in 1919 did not authorize Congress to prohibit the production and sale of "intoxicating liquors." When Congress banned marijuana in 1937, it did so in the guise of the Marihuana Tax Act , a revenue measure that authorized onerous regulations ostensibly aimed at collecting taxes on production and distribution, with severe penalties for noncompliance. But by the time marijuana prohibition was incorporated into the Controlled Substances Act of 1970, there was no need for such subterfuge. Instead Congress relied on its constitutional authority to "regulate commerce with foreign nations and among the several states."

The Commerce Clause, which was part of the original Constitution, did not change between 1937 and 1970. But beginning with a series of New Deal cases, the Supreme Court stretched its meaning to accommodate pretty much anything Congress wanted to do. In the 1942 case Wickard v. Filburn, for example, the Court said the Commerce Clause authorized punishment of an Ohio farmer for exceeding his government-imposed wheat quota, even though the extra grain never left his farm, let alone the state.

The Court went even further in the 2005 case Gonzales v. Raich, ruling that the federal government's power to regulate interstate commerce extends even to homegrown marijuana used for medical purposes by a California patient in compliance with state law. That decision, unlike Wickard, applied not just to production but to mere possession. According to the Court, the Commerce Clause encompasses the tiniest trace of marijuana in a cancer patient's drawer. "If Congress can regulate this under the Commerce Clause," observed dissenting Justice Clarence Thomas, "then it can regulate virtually anything—and the Federal Government is no longer one of limited and enumerated powers."

Many conservatives who pay lip service to the Constitution and the system of federalism it is supposed to protect nevertheless seem comfortable with this audacious assertion of congressional authority. In fact, they complain that the Obama administration is not using the Controlled Substances Act to shut down the newly legal marijuana markets in Colorado and Washington. Either they do not really believe in federalism or they cannot think straight when they smell marijuana.

Marijuana Prohibition Is Unjust

Even if marijuana prohibition were consistent with science and the Constitution, it would be inconsistent with basic principles of morality. It is patently unfair to treat marijuana merchants like criminals while treating liquor dealers like legitimate businessmen, especially in light of the two drugs' relative hazards. It is equally perverse to arrest cannabis consumers while leaving drinkers unmolested.

Peaceful activities such as growing a plant or selling its produce cannot justify the violence that is required to enforce prohibition. In the name of stopping people from getting high, police officers routinely commit acts that would be universally recognized as assault, burglary, theft, kidnapping, and even murder were it not for laws that draw arbitrary lines between psychoactive substances.

The main justification for those laws is protecting people from their own bad decisions. The hope is that prohibition will deter a certain number of people who otherwise would not only try marijuana but become self-destructively attached to it. Toward that end, police in the United States arrest hundreds of thousands of people on marijuana charges each year—nearly 700,000 in 2013, the vast majority for simple possession. While most of those marijuana offenders do not spend much time behind bars, about 40,000 people are serving sentences as long as life for growing or distributing cannabis. And even if marijuana offenders do not go to jail or prison, they still suffer public humiliation, legal costs, inconvenience, lost jobs, and all the lasting ancillary penalties of a criminal arrest.

Note that the people bearing these costs are not, by and large, the people who receive the purported benefits of prohibition. The person who, thanks to prohibition, never becomes a pathetic pothead goes about his life undisturbed while other people—people who never hurt him or anyone else—pay for the mistakes he avoids. Even paternalists should be troubled by the distribution of these burdens.

I am not a paternalist, because I do not believe the government should be in the business of stopping us from hurting ourselves. I am with John Stuart Mill on this:

The only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others. His own good, either physical or moral, is not a sufficient warrant….Over himself, over his own body and mind, the individual is sovereign.

Marijuana prohibition, along with the rest of the war on drugs, is a flagrant violation of this principle. It is a moral outrage built on a mountain of lies.

This article originally appeared at Forbes.com.