No government has ever created a commercial pot market. But next week voters in Colorado and Washington State are poised to do just that, passing ballot initiatives that legalize, tax, and regulate marijuana much like alcohol. Both efforts are polling above 50 percent, but regardless of whether they pass, the country is bending toward historic reforms and the remaining prohibitionists are on the run.

Only about one in three Americans think pot should remain illegal, and that shrinking block of opposition is poorly organized and underfunded, producing no formidable spokesperson, not even a sad-sack orator to argue futilely, that legalization is the devil’s work. “It’s actually hard for us to find people to debate,” says Rob Kampia, cofounder of the Marijuana Policy Project, a leading national reform organization. “I think a lot of folks have given up.”

But such a profound policy shift deserves a two-sided debate. And, yes, despite the gin-clear failures of prohibition and the face-raking lies told about marijuana in the past, there remains a prohibitionist case to be made. This much is obvious: the upsides of legalization have been wildly oversold, and the potential downsides blithely ignored. I’d like to correct that balance, not because I support prohibition but because I think legalization should succeed or fail on the merits, as much as they can be known.

Perhaps the best neutral source on the subject is “Marijuana Legalization: What Everyone Needs to Know,” published earlier this year by Oxford University Press. The book is the work of four scholars who collectively bring nearly 70 years of experience to the issue. Because there is no “objective” choice on marijuana policy, they provide a stew of good data and best guesses: the raw material for an honest, logical debate they hope will benefit all sides. In the end, however, the prohibitionist side seems to benefit most of all.

The case against legalization begins with a defense of its opposite: the benefits of prohibition. Reformers sometimes say prohibition is pointless, because everyone who wants to use pot already does. But as state laws have softened, pot use has risen sharply. More than three million people started smoking it regularly in the past five years, and the rate of high-school experimentation is at a 30-year high. One in 15 high school seniors are smoking daily or near daily. And when a kid first lights up at about age 16, it’s usually not with a cigarette.

Prohibition prevents an even more tremendous uptick, according to “Marijuana Legalization.” Remove it and you can expect a doubling or even tripling of the existing market, a spike to levels far surpassing any on record, and this in a country that already consumes the plant at three times the global average. What would be the health and welfare cost of such an explosion? The honest answer is: we don’t know. No one actually knows what legalizing marijuana will do to adult use, teen experimentation, and public health and safety overall. No one knows because no modern society has ever tried it.

We know enough, however, for serious concern. The mantra of marijuana legalization is “Safer than Alcohol,” which—to be fair—is generally true. But safer than alcohol is not the same as “safe.” Every year about 375,000 people end up in the ER with marijuana-related “averse reactions,” more than any drug other than cocaine. Some of those cases are the result of multiple drug interactions, where marijuana gets the blame while cocaine does the damage. But for many tens of thousands of ER visits marijuana is the only drug mentioned. And there’s even data suggesting that, as the authors of “Marijuana Legalization” put it, “marijuana can kill.” Between 1999 and 2007, the Centers for Disease Control, somewhat curiously, attributed 26 deaths to cannabis use—half in the subcategory “dependence.”

But at least pot isn’t addictive, right? Wrong. More than 4 million people self-report behavior that meets the clinical criteria for marijuana dependency or abuse. The “capture rate,” as scholars call it, was once about 9 percent, according to one study, but for people who start before age 25—as almost everyone does today—it jumps to 15 percent, the same capture rate as alcohol and just a percentage point less than cocaine. Drug treatment programs for marijuana have fives times the number of enrollees as they did just two decades ago. Most are referred by the U.S. criminal justice system, but many are not—and enrollment has more than doubled in European and Australian programs as well.

The most common explanation is that pot has grown more potent over that period. In the 1960s and ’70s, the percentage of THC (the stuff that gets you high) in good bud was usually less than 10 percent. Today, it’s often 15 percent and higher, with average potency more than doubling since the mid-1990s, according to tests run on seized pot.

Marijuana has also become more variable, coming in hundreds of strains and edible forms. One medical marijuana company makes a chocolate truffle with 60 times the THC of a joint. Others make hash, hash oil, and specialty bud with more than 25 percent THC. This isn’t automatically a problem, especially if potency means people use less to get high. But it’s hard to judge whether your first truffle has hit the spot before you have an urge to eat another. And a greater percentage of THC means a greater high—so much greater that the Netherlands has proposed policing all products with 15-percent-THC-and-up like “hard drugs.”

This high potency pot is pricey, and comprises only a fraction of the existing black market. But, again, that’s only because of prohibition. If legalization were passed, high potency products would probably fall in price and blanket the market, according to “Marijuana Legalization.” That’s worrying because even studies of low-power pot use—the only kind of studies available—show significant risks, especially for young people. Research released this past summer connected teenage pot use to a permanent drop in IQ between the first puff and early middle age. Other emerging literature suggests that pot use elevates the risk of schizophrenia and psychotic symptoms.

Besides harming themselves, pot users also put others at risk: driving high raises one’s likelihood of crashing—and driving with a little booze and little pot is much more dangerous than driving with either alone. Marijuana use may also have measurable domestic costs. Only two holidays a year show a spike in sudden-infant-deaths: New Year’s Day is one, and the other is the day after 4/20, when pot use is celebrated.

Finally, there are the long-term ramifications of legalization. Under prohibition, marijuana is an out-of-sight product with little branding and virtually no advertising. Expect that to change. The alcohol and tobacco industries traditionally get 80 percent of their profits from heavy users, and there’s every reason to believe that marijuana sellers would need at least the same ratio. That means the pot business could be the basis for a third huge, blood-sucking vice industry, dependent on converting kids and supporting heavy users. “If we create a licit market,” write the authors of “Marijuana Legalization,” “we should expect the industry’s product design, pricing and marketing to be devoted to creating as much addiction as possible.”

Is there anything good that would come with legalization? Reformers argue that legalizing weed would goose the economy, free law enforcement resources to pursue more serious crime, and unclog the criminal justice system. They say it would empty prisons and undercut the black market. The problem is: none of this is necessarily true.

Start with the economics. Marijuana is not America’s largest cash crop, contrary to a boast so widely repeated it’s assumed to be true. The value at the farm-gate is no more than $4.3 billion, or “somewhere between almonds and hay,” according to authors of “Marijuana Legalization.” Sales would skyrocket with legalization, but prices would plummet, deflating the overall market value. Bottom line: pot’s not the new corn.

It’s also not a surefire tax winner. The proposed tax is between $30 and $60 an ounce. Tobacco tax evasion is rampant at a fraction of that rate. And even if all the tax dollars came in, much of it would go not to schools or other worthy programs but to the costs of regulating and enforcing the new marijuana law. Lastly, because legal pot would be so easy grow, its job-creating power would be weak. It probably wouldn’t support more than 15,000 growers and an army of minimum-wage service workers—not the kind of jobs someone touts on the campaign trail.

As for the war on pot, it’s just not as high stakes as you might assume. About 750,000 people are arrested on possession charges every year, a howlingly large number. But virtually none of those folks end up in prison. Fewer than 400 people are serving state or federal sentences for marijuana possession alone, and many of those people plead down to that charge, or have serious histories of violence. Legalization wouldn’t mean the end of marijuana arrests either, because police will still be called on to enforce the new laws, just as they do with alcohol. And it wouldn’t mean the end of the Mexican gangs, which, contrary to another common boast, are diversified enough to survive entirely without marijuana profits.

And yet despite all this I still am not a prohibitionist. As the Seattle Times recently put it in an editorial endorsing legalization in Washington State, the relevant question isn’t whether marijuana is good: “It is whether prohibition is good. It is whether the people who use marijuana shall be subject to arrest, and whether the people who supply them shall be sent to prison. The question is whether the war on marijuana is worth what it costs.”

Quite obviously, the answer is no. In fact, of all the available options the status quo of arresting hundreds of thousands of people—most of them nonwhite, poor, and in for a world of collateral damage as a result of their arrest—is probably the least attractive choice, worse only than full legalization. The better decision is incremental reforms at the state level and a hands-off approach from the feds. Let people grow pot, and sell it, but not for profit, and without advertising, and in a tightly regulated marketplace. Tinker every year, adding new provisions and privileges as much needed new research comes in. And always update the law with a sunset provision. That way the process can’t be hijacked by lobbyists and special interests—and only one thing goes up in smoke.