Decades into the war on drugs, the world doesn't have much to show for it. The US is now in the middle of an opioid painkiller and heroin epidemic that has killed tens of thousands each year, despite tough-on-crime policies enforced under the drug war. Mexico has suffered from tens of thousands of deaths annually as the black market for drugs finances drug cartels that are so powerful they can wage war against governments and conquer cities. And drug use and trafficking haven't declined by an appreciable amount for decades.

These circumstances led more than 1,000 world leaders, including Bernie Sanders, to call for an end to the "disastrous" war on drugs in a recent letter to UN Secretary General Ban Ki-moon.

But what exactly does it mean to end the war on drugs?

Surely, almost no one wants to see cocaine or heroin sold at CVS. Some of the letter's signatories, such as Sanders, are just now coming around to marijuana legalization. It's hard to imagine they're willing to go much further with more dangerous drugs.

At the same time, there is a great interest in pulling back or eliminating some of the unintended consequences of the drug war. In the US, the focus typically falls on the incarceration of nonviolent drug users and militarized expansion of police powers.

Around the world, the war on drugs has an even more destabilizing impact: It creates a black market for drugs that finances criminal groups' violent operations, especially in poorer countries where drugs are produced and trafficked to wealthier nations (like the US). And this market is so lucrative that criminal groups are willing to go to war over it.

But is it actually possible to draw back the harsh, punitive criminalization of drugs in America without ending up at full commercial legalization and gravely risking public health?

Through interviews with some of the world's smartest drug policy experts and my review of the research, I put together three of the best ideas on dismantling the current system. These are by no means the only options for ending the war on drugs. But they are the ones that seemed, based on my reporting on the issue and data, to have the most merit.

There were some points of agreement. Experts agreed that, regardless of how legal regimes change, countries should boost public health programs for drugs, including treatment and prevention. And whether drugs have medical use, such as marijuana or hallucinogens, is also something that can be evaluated separately.

But there was a lot of disagreement about what legal regimes for drugs should look like. So here are the three plans that came from my conversations.

Approach 1: Pull back harsh enforcement, but keep criminalization

The most restrictive approach, from drug policy expert Jon Caulkins at Carnegie Mellon University, would potentially scale back the enforcement of some drug crimes to eliminate excessive penalties for nonviolent drug offenders, while keeping criminalization in place to, in theory, keep drugs less accessible.

The idea is that the severity of punishment doesn't matter much to stopping drug use. A 2014 study from Peter Reuter at the University of Maryland and Harold Pollack at the University of Chicago found there's no good evidence that tougher punishments or harsher supply-elimination efforts, such as crop eradication, do a better job of pushing down access to drugs and substance abuse than lighter penalties. So increasing the severity of enforcement or punishments doesn't do much, if anything, to slow the flow of drugs.

But the simple act of making something illegal does make drugs more expensive and less accessible, Caulkins said. His 2014 study suggested that prohibition multiplies the price of hard drugs like cocaine by as much as 10 times. And illicit drugs obviously aren't available through easy means, since drugs aren't easily sold. So the drug war is likely stopping some drug use: Caulkins estimated that legalization could lead hard drug abuse to triple or more.

Still, Caulkins said, "There's a lot of opportunity for rejiggering enforcement to get the whole mindset shifted from 'let's maximize the amount of punishment inflicted' to 'let's minimize the amount of punishment inflicted subject to the constraint that we do suppress the flagrant [drug] markets.'"

"There's a lot of opportunity for rejiggering enforcement to get the whole mindset shifted"

Caulkins said the idea is that the public will clearly signal to law enforcement that they only want police and prosecutors to go after drug dealers and traffickers, especially violent ones, but not users. He believes police can be trusted with this kind of discretion, without any changes to the law, as long as they get clear guidance on priorities from the public.

Caulkins acknowledges that this idea would run into a major criticism: Many people believe that police can't be forced to act less punitive unless policies change.

That belief is one driver for support for decriminalization, when harsher criminal penalties (jail or prison time) are replaced with a civil fine for possession of small amounts of drugs. Supporters argue that since the research shows severity of punishment doesn't much matter, keeping drugs illegal but decriminalizing small amounts of them could maintain the benefits of prohibition (making drugs less accessible through illegality) but also cut down on arrests of nonviolent drug users.

But Caulkins argued against using the research on severity of punishment to support decriminalization. "It is possible to over-learn that story," he said. "If you switch from something truly being a crime to something having a $10 ticket — like if robbery were only punishable by a $10 civil ticket, like a parking ticket — that might make a difference to some robbers."

Caulkins said decriminalization could make it much harder to crack down on drug dealers, because law enforcement often uses simple possession laws to go after dealers when they can't prove an intent to sell. "It will complicate enforcement against sellers at the retail level," he said. "Sellers at the retail level are not so often observed to be in the process of making a sale. Often, the sellers get arrested for possession, because they are possessing the amount they're out there to sell. So decriminalizing possession makes it harder to enforce against retail sellers."

"[Decriminalization] will complicate enforcement against sellers at the retail level"

So if law enforcement can continue using possession crimes to go after dealers, then they can be kept off the streets — and not engage in the violence and turf wars that tend to come with outdoor drug markets.

Caulkins also worries that decriminalization could lead to more drug use in general. If this holds, decriminalization could actually make drug-related violence worse — since demand (and subsequently the profitability) of drugs would go up, making them more lucrative for violent criminal groups.

The data on this is mixed. After Portugal decriminalized all drugs in 2001, the country saw a decrease in drug-related deaths and drops in reported past-year and past-month drug use, according to a 2014 report from the Transform Drug Policy Foundation. But it also saw an increase in lifetime prevalence of drug use, as well as an uptick in reported use among teens after 2007.

Caulkins said these statistics are weak, since they don't control for other variables. So it's possible that decriminalization pushes up drug use, but other factors — changing cultural fads and other policies — push down use more than decriminalization pushes it up.

For example, when Portugal decriminalized drugs, it also adopted special commissions that attempt to connect drug addicts to treatment. Although the success of these commissions has yet to be thoroughly evaluated, it is possible that even as decriminalization increased drug use, the commissions and more access to treatment got so many people off drugs that drug use still fell overall.

The uncertainty makes Caulkins, who characterizes himself as "a worrier" and "a father of teenagers," cautious of moving too far ahead with relaxing drug laws. So he prefers, instead, to tweak the current model instead of moving too far away from it.

Approach 2: Decriminalization, smart prohibition, and smart legalization

Another possibility is to pull back the drug war even further through decriminalization, but significantly alter how governments enforce prohibition and regulate legal drugs.

Mark Kleiman, a drug policy expert at the New York University's Marron Institute, calls this approach "smart prohibition" and "smart legalization." "Smart prohibition would try to maintain the gains we have made in terms of drug abuse compared to the legal market with as little ancillary damage as possible," he said. "And smart legalization would try to eliminate the ancillary damage with as little harm on the public health side as possible."

Kleiman elaborated on the two pillars:

Smart prohibition would focus on penalizing and preventing problematic behaviors and actions surrounding drugs, rather than punishing mere drug use. For example, drug users could be punished for repeatedly stealing things to pay for a drug habit, but they would not be strictly punished if their drug habit was not harming anyone. And to the extent someone is punished, sentences would be generally lower and not carry as many punishments after jail or prison time (so convicted drug offenders wouldn't be barred, as they are today, from obtaining student loans or voting).

would focus on penalizing and preventing problematic behaviors and actions surrounding drugs, rather than punishing mere drug use. For example, drug users could be punished for repeatedly stealing things to pay for a drug habit, but they would not be strictly punished if their drug habit was not harming anyone. And to the extent someone is punished, sentences would be generally lower and not carry as many punishments after jail or prison time (so convicted drug offenders wouldn't be barred, as they are today, from obtaining student loans or voting). Smart legalization would allow the use and sales of certain drugs, while minimizing the commercialization of legal drugs — by, for example, putting the state government in charge of drug sales or only allowing nonprofits to sell drugs.

Generally, smart prohibition would apply to all the illicit drugs except marijuana and hallucinogens, and smart legalization would apply to alcohol, tobacco, marijuana, and hallucinogens.

In defense of this, Kleiman cites the research that shows harsher punishments don't deter criminal behavior much more than simply making something illegal does. "You need to distinguish between the effects of prohibition and the effects of enforcement," he said. "You'd be able to get a lot of the benefits of prohibition with relatively mild enforcement."

In terms of actually accomplishing smart prohibition, small amounts of drug possession for any drug would be outright legalized to prevent the arrest of simple drug users. But trafficking and selling drugs would remain illegal to prohibit the establishment of legal markets that could increase access to drugs. And special systems would be put in place to discourage problematic drug-related behavior.

Kleiman cited the 24/7 Sobriety Program that's seen success in curtailing alcohol abuse in South Dakota. The program effectively revokes people's right to drink if a court deems it necessary after an alcohol-related offense, such as drunk driving. To enforce this, officials monitor offenders through twice-a-day breathalyzer tests or a bracelet that can track blood alcohol level, and they jail offenders for one or two days for each failed test. Studies from the RAND Corporation have linked the program to drops in mortality, DUI arrests, and domestic violence arrests.

"You'd be able to get a lot of the benefits of prohibition with relatively mild enforcement"

Although this program has been applied to alcohol, it could also be used for legal and illegal drugs. Kleiman emphasized that this should not be used only for drug use — but rather people whose drug use has led to bad behavior, like intoxicated driving, theft, or violence.

Kleiman's hope is to use these programs to ensure someone isn't engaging in harmful drug use, while letting social controls and public health programs address if someone has addiction and needs to be treated for it.

Meanwhile, Kleiman said the drugs that are already legal — and substances that would become legal under his plan, such as marijuana and hallucinogens — would be strictly regulated. "Smart legalization would look a bit like what we're doing with tobacco today," he said. "Yeah, this stuff is legal, but it's not really okay."

Generally, tobacco enforcement would remain the same — with high taxes, restrictions on sales and marketing, and so on. There would be one difference: The regulations and taxes on e-cigarettes could be purposely lower, since these devices seem to be much safer than their combustive counterparts. This would hopefully push people to a safer form of consuming nicotine.

Alcohol and marijuana would be sold in much more regulated outlets than they are today, with a focus on limiting marketing to stop for-profit companies from pushing the heaviest drug users to use even more alcohol or pot. (One of Kleiman's favorite ideas is to let people set quotas for how much of a drug they can buy. So someone would say, for instance, that they can only buy 40 grams of marijuana a month, and after that amount vendors wouldn't be allowed to sell anymore to that person. "This is to give your long-term self a fighting chance against your short-term self," Kleiman said.)

"Smart legalization would look a bit like what we're doing with tobacco today"

As for psychedelics, these drugs would only be available to buy and use in licensed and regulated facilities with supervisors that can guide someone through their experience. This would, hopefully, mitigate the chances of an accident or bad trip, while letting people take drugs that can lead to serious therapeutic benefits. (For more on how this would work, check out Vox's explainer.)

All of this, Kleiman said, could be paired up with public health programs that should be by and large free from the criminal justice system. So whether the country ramps up prevention, treatment, and harm reduction programs — such as clean needle exchanges, easier access to the opioid overdose antidote naloxone, or medication-assisted treatment like methadone and Suboxone — should be left to the health care system, not police and courts.

One gap in Caulkins's and Kleiman's plans is they would leave fairly large black markets for drugs in place, and these markets have fueled huge levels of violence around the world, particularly in Latin America, over the past several decades.

Kleiman argued that this could be largely addressed by demilitarizing anti-drug policies. That seems plausible: Although Mexico has always dealt with some drug-related violence, its conflict wasn't as bloody and deadly as it is now until President Felipe Calderón in 2006 declared a ramped-up, militarized drug war, with significant amounts of US aid through the Mérida Initiative. The result: One study found life expectancy for men in the country dropped for the first time in decades. So a reversal of militarization could undo much of this escalation in violence.

Governments could also signal to criminal groups that while they will generally prohibit drug trafficking, they will really prohibit drug-related violence through much harsher enforcement. Over time, this could encourage drug trafficking groups to avoid violence.

Still, it's true that many countries have dealt with drug-related violence before they militarized their conflicts, and the incentive to avoid violence — to avoid government attention — has always existed. To address much of the violence, then, some argue drug policy may need to go even further.

Approach 3: Legalize and tightly regulate all drugs

The most radical approach — and one most Americans don't agree with — is legalizing and regulating all drugs. This is something no country has done in modern times, as many recreational drugs remain illegal to sell virtually everywhere in the world. So it's difficult to say for certain what would happen.

Still, there was one consistent group that drug policy experts and historians pointed me to when I asked whether anyone had a realistic legalization model: the Transform Drug Policy Foundation. While many don't agree with Transform's plan, it was consistently cited as the most detailed, evidence-based proposal.

Explaining his approach, Steve Rolles, senior policy analyst for Transform, said his group applied what we already know about other vice markets — particularly alcohol, tobacco, and gambling — to illegal drugs.

To be clear, this would not mean letting people buy any drug they want at the grocery store. "Different drugs would be regulated in different ways," Rolles explained. "The determinant of how you would regulate a drug would be what the risks and behaviors associated with that particular drug were. So the more risky a drug is, clearly, the more justification you have for more intrusive or intense regulation."

In its very detailed blueprint, Transform lays out its regulatory models based on tiers that ramp up restrictions based on a drug's dangers. Here's a quick summary of the five tiers, which divide up where and how the drugs would be available based on how potentially dangerous they are:

Medically supervised venues: Drugs put in this category, including heroin or amphetamines, would only be allowed with a prescription (typically for people with drug use disorders) and the direct supervision of a trained expert, like a doctor in a controlled facility.

Drugs put in this category, including heroin or amphetamines, would only be allowed with a prescription (typically for people with drug use disorders) and the direct supervision of a trained expert, like a doctor in a controlled facility. Pharmacies: Drugs in this tier, such as MDMA, powder cocaine, or amphetamine, would only be dispensed through pharmacies with a prescription or over the counter. While it is currently the case that pharmacies focus on medical applications, the blueprint suggests that pharmacists could also act as trained and licensed gatekeepers for drugs used in recreational settings.

Drugs in this tier, such as MDMA, powder cocaine, or amphetamine, would only be dispensed through pharmacies with a prescription or over the counter. While it is currently the case that pharmacies focus on medical applications, the blueprint suggests that pharmacists could also act as trained and licensed gatekeepers for drugs used in recreational settings. Licensed sales: Drugs in this classification, like marijuana and stimulant-based drinks, would be dispensed by licensed, regulated vendors. These sellers don't have to be for-profit entities; they could be nonprofits or government-controlled.

Drugs in this classification, like marijuana and stimulant-based drinks, would be dispensed by licensed, regulated vendors. These sellers don't have to be for-profit entities; they could be nonprofits or government-controlled. Licensed premises: These regulated establishments would dispense drugs, such as smoked opium, psychedelics, or poppy tea, much like alcohol is sold and consumed in bars today — although in some cases, as with psychedelics, the vendors would need training to help guide people through their experiences.

These regulated establishments would dispense drugs, such as smoked opium, psychedelics, or poppy tea, much like alcohol is sold and consumed in bars today — although in some cases, as with psychedelics, the vendors would need training to help guide people through their experiences. Unlicensed sales: Drugs in this category, like coca tea, would be available easily, much like caffeine.

Rolles emphasized that commercialization should be avoided. So even the drugs that are more accessible could still fall under strict regulations, such as a ban on marketing, taxes to keep the prices high, and even price controls. This could make up for at least part of the price drop that comes with the end of prohibition.

The new regulations could also be applied to alcohol and tobacco, as well as marijuana in states that already legalized the drug. (Rolles said he doesn't like that marijuana is moving to a commercialized legal model in parts of the US.)

But why go for legalization and regulation? There are two main reasons for this, Rolles argued: One, it completely eliminates the black market for drugs that enables so much violence around the world, particularly Latin America. Two, it could potentially make drug consumption safer.

The first point is relatively uncontroversial. It is clear that the war on drugs has had an enormously negative effect in several countries around the world, particularly Mexico in recent years. Again, a study found that violence from the drug war caused Mexico's life expectancy to stagnate — and, in men's cases, drop — after decades of increases.

On the second point, Rolles argues that legalizing and regulating drugs could make for safer drug use. So if people get their drugs from a regulated source, governments can ensure there's nothing that would make an already dangerous substance even more dangerous (such as fentanyl in heroin).

It may also eliminate the incentives in the black market to make drugs as potent as possible, since in a black market it's much easier to smuggle a highly potent pound of a drug (such as heroin) than it would be to smuggle a few pounds of something that's not as potent (such as smoked opium).

A similar black market phenomenon occurred during Prohibition, when the US banned alcohol from 1920 to 1933. During Prohibition, the market quickly went to spirits. After Prohibition, it has shifted toward wine and beer.

"The less risky, less potent products are more available, and the higher risk products are increasingly less available or not available at all"

Using heroin as an example, Rolles argues that many opioid users could satisfy their desires by smoking opium. But because the illicit market has moved toward the much more potent heroin, they largely don't have that option. So under Transform's model, smoked opium would be more accessible than heroin — in what Rolles calls harm reduction, since it acknowledges people are going to use drugs anyway but pushes them toward doing the safer version of those drugs.

"The idea that we're trying to promote in the blueprint is that a regulatory model can tilt the market the other way," Rolles said. "So the less risky, less potent products are more available, and the higher risk products are increasingly less available or not available at all."

Of course, this runs the risk of getting people hooked on the less harmful substances and leading them to progress to harder drugs. So someone could start on opium, because it's now potentially more accessible, and eventually climb to heroin. This is similar to what's happened with the opioid epidemic, in which some people went from opioid painkillers provided by doctors to the more potent opioids heroin and fentanyl.

But if someone does get hooked on heroin, Rolles said this could be safer under legalization — since heroin would be available in controlled venues, where users would have access to clean needles (without a risk of HIV or hepatitis infection), and supervisors would have access to naloxone, which reverses opioid overdoses. In several countries, these kinds of injection sites for drug users who prove resistant to treatment have been credited with reductions in drug-related crimes and overdoses, as well as improvements in social functioning through stabilized housing and employment.

Rolles acknowledges Transform's model won't fix every problem related to drugs. But he said it could lead to better results: "All regulation can do is to reduce the harms associated with the market and harms associated with using behaviors. We have to be realistic about what we can achieve. Legalization and regulation does not get rid of the drug problem. It doesn't necessarily deal with addiction. It doesn't stop people dying from drugs. But it may reduce harms; it may reduce deaths. It just won't eliminate them."

The big takeaway: Drug policy is a balancing act

As you can probably tell from the diverse opinions, it's still not clear which drug policies may be best for the United States and the rest of the world. It's possible the final solution may not even be one of these three plans, and governments may land on a different solution after tinkering with all sorts of policies — if they choose to end their drug wars at all.

But whatever policy prescription governments land on, even if it's one of the three plans above, there will always be drawbacks and risks.

For one, anything short of legalization would likely fail to address all or perhaps most drug-related violence in the developing world, even if countries do demilitarize their anti-drug policies. After all, drug trafficking organizations always fought among themselves. So while the escalation and militarization of the war on drugs in Mexico did lead to much more violence, it was in part exacerbating an already-bad situation. (There is also the question of whether the genie can be put back in the bottle now that drug cartels are built to be highly violent.)

But with legalization, it's unclear if the US can actually sustain a strict regulatory model for dangerous drugs, since the country simply doesn't have a good track record for doing this with already legal substances.

Anything short of legalization would likely fail to address all or even most drug-related violence

Consider what happened after Prohibition when the US ended its short-lived ban on alcohol: Many states ended their bans by creating tightly regulated models for alcohol. But these models fell apart over time as big alcohol companies lobbied states to loosen their regulations, particularly by pressing them on the potential tax revenue and jobs that could come if the private market took over and was allowed to flourish. Now 88,000 deaths each year are linked to alcohol, on top of the many non-deadly accidents, illnesses, and poisonings that occur as a result of booze.

(It's worth noting that Prohibition appeared to reduce alcohol consumption and some forms of alcohol-related deaths, at least temporarily. A 2003 study from economists Angela Dills and Jeffrey Miron found Prohibition likely reduced liver cirrhosis deaths by about 10 to 20 percent. But that didn't, according to experts, outweigh the rise in violence and crime that surrounded the black market for alcohol during Prohibition. This conflict between public health and safety is essentially the same debate we're having today with other drugs.)

Or consider what's happened with the opioid epidemic. In the 1990s, companies like Purdue Pharma pushed their opioid painkillers on doctors and patients through a very aggressive marketing campaign. Doctors, who were concerned with treating pain as a serious medical issue, prescribed the drugs in huge droves, letting them proliferate. As a result, the US is in the middle of an opioid epidemic — one that has led to people using stronger, more dangerous opioids, like heroin and fentanyl — that's killing tens of thousands a year.

All this time, one would expect a regulatory body, like the FDA or DEA, to step in and stop the proliferation of dangerous medications. But they only did so after tens of thousands of deaths. Regulation failed.

Something similar could happen with newly legal drugs. Once big companies get a taste of selling poppy or coca tea, they could start lobbying for the ability to sell more of their products or even cocaine and heroin. Given how powerful alcohol and pharmaceutical companies have proven to be, it's not totally unfeasible that coca or opium companies couldn't similarly succeed. And that could lead to tens of thousands of drug deaths — except under legalization, Americans may be desensitized to these deaths, much like they have been for alcohol.

The big counterpoint to commercialization supplanting public health interests is how America has responded to tobacco. Here, the US has sustained a fairly strict regulatory approach toward a big for-profit industry, largely thanks to pressure from public health groups and Americans who were furious at the way the tobacco industry had gotten so many people hooked and killed. It is possible — even likely — that a similar sentiment toward hard drugs like heroin or cocaine would sustain a very strict regulatory approach. After all, it's hard to imagine mainstream America ever embracing these clearly risky drugs.

At the same time, the US only adopted a harsher approach to tobacco after the tobacco industry created one of the biggest public health crises in the country's history. And 480,000 Americans still die each year due to tobacco. It shouldn't take a huge death toll to get regulation in motion, but that's what tobacco — and now opioids — required.

All of this is to say that the best approach may be to proceed with caution. The war on drugs slowly ramped up over decades, from the prohibit-through-taxes model of the early 20th century to President Richard Nixon's declaration of the modern drug war to President Ronald Reagan's incredibly punitive, militarized escalation. Similarly, its end may come over time through incremental reforms.