When world leaders met in the 1960s, '70s, and '80s to lay out the war on drugs, there was broad international agreement that drugs were a global menace that must be stopped by any means necessary — particularly through the heavy hand of police and military might.

A few decades later, that consensus is vanishing. On one end of the spectrum, some countries have moved toward decriminalization of drugs — and even the legalization of marijuana — as well as focusing on harm reduction instead of outright prohibition. On the other end, some countries still execute their citizens for drug trafficking. (And, of course, many nations are in between.)

This week, the United Nations is holding a meeting that could finally reflect the deep disagreement around the world on the correct approach to the war on drugs — in a special session that drug policy reformers say could prove one of the most significant UN meetings on drugs in decades.

The meeting will not officially change the international conventions that have since the 1970s pushed for a criminal justice approach to drugs. But the outcome document world leaders will adopt will reflect on the drug war's future. At the very least, the document and debate around it have shown that the world is no longer as united on drugs as it once was — and that could make it harder to establish international drug control policies in the future.

The meeting is supposed to help guide international drug policy

The meeting won't explicitly change international law regarding drugs, but reformers hope that it will help set the tone for future international meetings about drug policy.

The way this meeting was called shows the urgency with which some countries view this problem. The next UN General Assembly Special Session on Drugs (UNGASS) was supposed to be in 2019. But in 2012, the presidents of Colombia, Guatemala, and Mexico asked to hold a special meeting in 2016 to discuss drug policy reform. (All three of these nations have been ravaged by drug-related violence, which is fueled by the black market for drugs that effectively finances violent criminal organizations around the world. So it's in their interest to seek reform that could alleviate the violence.)

But what does the UN have to do with drugs? Well, almost all countries' drug laws are shaped by three major international drug treaties: the Single Convention on Narcotic Drugs of 1961, the Convention on Psychotropic Drugs of 1971, and the UN Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances of 1988. Combined, the treaties require participating countries to limit and prohibit the possession, use, trade, and distribution of drugs outside of medical and scientific purposes, and work together to stop international drug trafficking.

There is some debate about whether these treaties prohibit drug decriminalization — when criminal penalties are repealed but civil ones remain in place — and medical marijuana legalization. But one thing the treaties are absolutely clear on is that illicit drugs aren't to be allowed for recreational use, and certainly not for recreational sales.

Reformers hope that the outcome document could provide a first step to reforming the treaties to allow more flexibility in countries' drug policies. The document essentially follows up on previous UN drug meetings — including a now widely mocked 1998 meeting that met under the slogan, "A drug free world: We can do it!" — to evaluate the progress of the war on drugs.

The final draft of the outcome document has disappointed reformers, although they say it's a general step forward

As Jasmine Tyler, a senior policy analyst at the liberal Open Society Foundations, told me, "This meeting is a really great opportunity for the global community to just recognize out loud that the punitive prohibitionist approach of the last 40-plus years has had some significant human rights costs and has really undermined democracy in some countries."

In the US, the focus on human rights abuses tends to be on the militarized expansion of police and incarceration of nonviolent drug offenders who need treatment, not jail or prison. But around the world, the war on drugs can have a much broader impact — by fueling drug-related violence that undermines entire governments, as has occurred in Colombia and Mexico over the past several decades. And in countries like Russia, the rejection of public health programs for drugs has fostered HIV/AIDS epidemics.

To this end, the final draft of the outcome document has disappointed reformers, although they say it's a general step forward compared with the old, punitive regime.

For example, the document explicitly avoids the phrase "harm reduction" — out of fear it could be misinterpreted as support for decriminalization and legalization by some of the more punitive countries when it comes to drugs, such as Russia or China.

(The phrase is typically used to describe policies that embrace the reality that some people will use drugs but governments can do some things to make that drug use safer. Some examples: providing clean needles, to avoid HIV infection, or heroin-injection facilities, to ensure someone is watching over the heroin user to mitigate the risk of overdose.)

But even though the document avoids the phrase "harm reduction," it encourages countries to consider actual harm reduction policies:

Invite relevant national authorities to consider, in accordance with their national legislation and the three international drug control conventions, including into national prevention, treatment, care, recovery, rehabilitation and social reintegration measures and programmes, in the context of comprehensive and balanced drug demand reduction efforts, effective measures aimed at minimizing the adverse public health and social consequences of drug abuse, including, appropriate medication-assisted therapy programmes, injecting equipment programmes as well as antiretroviral therapy and other relevant interventions.

This kind of mixed messaging colors the entire document, reflecting a growing chasm in the international community over drugs.

Reformers want to address several big issues

Drug policy reformers want to tap into these growing divisions between countries over international drug policy to create more flexibility in international drug laws, as well as stop human rights abuses and close major medical gaps in poorer nations.

They acknowledge this will be a long process: After this week's meeting, the body will likely meet in 2019 to set a new action plan, as the body did in 1998 and 2009. It's possible the 2019 meeting could lead to more concrete discussions about redefining the international drug regimes, but whether those discussions will lead to actual changes in the international drug treaties — the big goal for reformers — could take years to resolve.

Nonetheless, there are some major areas where they hope to make progress. Here are some examples:

More flexibility for decriminalization, legalization, and harm reduction: The treaties are unclear on some drug policy issues, like decriminalization and harm reduction, and ban some approaches, like legalization for recreational use. Reformers say it's time to open up the treaties to allow for more flexibility, so countries can experiment with policies like legalization, decriminalization, and harm reduction approaches that may in the end better address drug abuse than strict criminalization. Abolish the death penalty for drug crimes: Some countries, including Indonesia, China, and Iran, still use the death penalty against drug traffickers. Reformers, many of whom come from European countries where the death penalty is outright illegal, see this as a shocking violation of human rights, because governments are essentially killing people for nonviolent offenses. So they want the death penalty abolished for drug crimes. Improve access to some drugs for medical purposes: Particularly in developing nations, some drugs, such as opioids for pain, remain inaccessible to patients. But that's also true to a lesser extent in developed countries, where drugs like marijuana remain difficult to research and largely illegal for medical purposes. Reformers wanted world leaders to acknowledge that this leaves some people suffering from diseases and conditions that we know how to treat, and change their laws to improve access.

The outcome document makes some progress on the third issue, emphasizing that this is something countries should take seriously. It makes a tiny bit of progress on the first issue by putting some emphasis on harm reduction efforts. But it makes no progress on the second issue — the death penalty — due to stringent opposition from China and Indonesia in particular.

Some of these issues apply directly to the US, particularly when it comes to medical marijuana, decriminalization, and legalization. And while the US doesn't use the death penalty for drug traffickers (unless they are involved in violent crimes), the discussion surrounding the right sentences for drug crimes — and whether people should be in jail or prison at all for drugs — applies to the US, which has harsh prison sentences for drug crimes and leads the world in incarceration.

Reformers are pushing for these changes in UN meetings. But they also plan to push for change through public protests, awareness campaigns, and other calls to action, such as a recent letter signed by more than 1,000 world leaders to end the "disastrous" war on drugs.

A recent letter signed by more than 1,000 world leaders called to end the "disastrous" war on drugs

Rick Lines, the executive director of Harm Reduction International, told me he's optimistic. Even on the death penalty front, which saw little progress despite his group's work, he said he sees trends headed in the right direction. "If you look back in the previous [documents], you typically get drugs described in the same language as you see terrorism described today," he said, noting that this type of language is absent from the 2016 draft. "That would hopefully indicate a shift in the … scare tactics framing of drugs."

But reformers acknowledge that progress is slower than they would like. One reason for that: The UN makes drug control decisions through consensus. So if UN members want to change the drug control treaties, every participating member has to get on board. Given that the world is a big and varied place, this makes it very difficult to get anything done.

Reformers argue that the simultaneous need for consensus and growing disagreement over the right approach to drugs poses a huge threat to the UN, with the potential to doom the international drug control regime altogether if nothing changes.

Without reform, the international drug control regime could collapse

Unlike many issues, a lack of progress toward reform won't necessarily mean that the status quo — a harsh, punitive war on drugs — will continue unabated. Instead, it is very much possible that without action the entire drug control regime will collapse, as rifts between nations on drug policy grow and some countries decide to move ahead with reform regardless of what the treaties say.

"It runs the risk of becoming outdated, because what we see is national policies are moving forward with or without the UN," said Hannah Hetzer, the senior policy manager of the Americas at the Drug Policy Alliance. "If the UN doesn't catch up to that or at least acknowledge in its debate that those things are happening and that they need to be looked at, then it runs the risk of becoming more of an irrelevant body on drug control."

No single issue signifies the divides in drug policy more than the death penalty. On one hand, you have countries that don't allow the death penalty for any crime and have outright decriminalized drug use. On the other hand, several big countries, including China, use the death penalty against nonviolent drug offenders. The big divide shows that the world is tremendously divided on how to tackle crime and drugs.

In some cases, the divisions and lack of progress are leading countries to move forward with reform even if their actions violate the treaties. Uruguay, for example, legalized marijuana for recreational use — something that is explicitly prohibited in the treaties. Canada, similarly, is going in that direction, with the new Liberal government promising to legalize marijuana.

We could eventually reach a point where many of the world's biggest leaders are explicitly violating the drug control regime

Even the US, which led the push for the drug control regimes that set up the modern international war on drugs, is quite close to violating the conventions. Four states and Washington, DC, have legalized marijuana for recreational uses — something that could violate the treaties. The US's defense: Marijuana is still illegal under federal law, so the country as a whole is still technically in agreement with the conventions. It's a pretty wonky argument — maybe technically right, but it seems phony when the country has a flourishing industry that sold $3.4 billion in legal pot in 2015.

If countries keep moving in this direction, we could eventually reach a point where many of the world's biggest leaders are explicitly violating the drug control regime. They all may have good reasons for doing that — by any measurement, international drug use and trafficking has not significantly decreased since the drug war began. So they feel like they have to move in a new direction, even without the global consensus that's needed to change the drug control conventions.

But even if they're in the right, having several major countries in violation of the drug control regime would undermine the whole system, potentially leading to its collapse. That would leave the world with no real international system for dealing with drugs.

But this is an issue that needs to be dealt with internationally — the flow of drugs is global, and the effects of those drug flows impact multiple countries at once.

For example, it's mostly citizens in relatively rich nations, like the US, that buy drugs. But the drugs themselves come from developing countries, like Mexico, Colombia, and Afghanistan, where growing marijuana, cocaine, or opium (for heroin) is often the best way to make ends meet. As a result, wealthier nations like the US generally struggle more with drug abuse, addiction, and overdose, while the developing countries sending drugs to the US end up dealing more with the brunt of the violence related to trafficking.

So regardless of whether the punitive war on drugs, decriminalization, or legalization is the right approach to drug policy, it's an issue that calls for international solutions. The drug control regime provides a necessary avenue to that global cooperation — but at this rate, it may not be around for much longer.