Though some US attorneys have said that they will not change their priorities in response— and there has been a huge political backlash—the threat of a crackdown will inevitably have a chilling effect on the nascent pot industry. While Congress still prohibits federal money being spent to interfere with medical weed in the states that have it, that provision expires on January 19, and may not be included in the next budget.

To understand just how counterproductive it would be to legally target weed right now, it’s worth looking closely at the growing body of data suggesting that pot may be preventing he opioid epidemic from being even deadlier. At least 11 studies have analyzed the effects of marijuana on opioid use for chronic pain, as well as its connections with opioid-overdose deaths and addiction rates. Ten of them found strong positive associations, meaning that more marijuana availability was associated with less harm from opioids.

For example, research published in JAMA Internal Medicine in 2014 analyzed the relationship between a state’s legalization of medical marijuana and its opioid overdose death rate, using data from 1999 through 2010 in all 50 states. It found that overall, medical cannabis legalization was associated with a 25 percent reduction in overdose deaths— and that the longer the laws were in effect, the greater the decline. Indeed, states that had such laws for six years saw a 33 percent reduction in fatalities.

“The fact that we are seeing decline of fatal overdose by 25 percent in states with legal medical marijuana, although it doesn’t show causation, it certainly shows a correlation that all of us need to stand up and take notice of,” said Dr. David Nathan, a distinguished psychiatrist and founder of Doctors for Cannabis Regulation, “It’s quite intuitive that cannabis, both as an adjunct to and replacement for opioids, would lead to a favorable outcome given that cannabis is much less toxic."

Another study, conducted by researchers at the nonpartisan Rand Corporation and published as a working paper for the National Bureau of Economic Research in 2015, found that medical marijuana availability was linked with reductions in both the opioid overdose death rate and the rate at which people sought treatment for opioid addiction. In states that had the greatest access to medical marijuana via dispensaries, treatment admissions related to opioids were reduced by 28 percent—while overdose death rates fell by 31 percent. Like the JAMA Internal Medicine study, this research also showed that the effect became larger over time.

A third study published in the American Journal of Public Health looked specifically at Colorado and found that its legalization of recreational marijuana sales in 2012 (it legalized medical marijuana in 2000, but did not have dispensaries until 2007) was connected with a 6.5 percent reduction in opioid related deaths. Another study in the same journal found that the percentage of drivers involved in car crashes with opioids in their systems declined among drivers between 21 and 40 in medical marijuana states.

Weed seems to substitute for opioids both when it comes to treating chronic pain and providing an alternative means of recreation for some who misuse painkillers. And while no one sane believes pot is a panacea that can completely replace opioids for pain or eliminate the need for maintenance medications in addiction treatment, there’s even more evidence that it can help reduce harm.

For example, 2016 study of the Medicare population published in Health Affairs found that having an effective medical marijuana law in place reduced the number of prescription pain relievers prescribed per doctor by just over 1,800 daily doses per year, compared to states without such laws. Reductions were also seen in prescribing of antidepressants and anti-anxiety medications, leading to an estimated $165 million in savings in 2013. A follow-up study last year suggested Medicare could save over $1 billion if all states made medical marijuana legally available.

Several research groups also interviewed chronic pain patients and medical marijuana users about which drugs they used medical marijuana to replace or reduce. One study surveyed nearly 3,000 pot smokers recruited at Washington dispensaries or via social media: 36 percent said they used marijuana to replace opioids; a Canadian study had similar findings.

Other researchers compared chronic pain patients who either did or did not access medical marijuana in New Mexico: the medical marijuana users were 17 times more likely to stop using prescription opioids, five times more likely to reduce their daily dose of opioids, and took opioid doses that declined by nearly half over the 21 month study period; those who didn’t use medical marijuana showed a slight rise in opioid dose. A study of 244 Michigan medical marijuana patients found a 64 percent decrease in opioid use following initiation of medical marijuana.

The only study I could find suggesting potential opioid-related harm linked to marijuana availability concluded that medical marijuana laws were associated with a rise in opioid mortality—but only if a state did not also have a prescription-drug monitoring database. Since all 50 states (Missouri had been the exception) have or will have such systems, it is not clear how relevant this kind of outlier is.

I’ve reviewed here only how marijuana access is linked with reductions in opioid-associated damage: I do not have space to examine the studies on how it has also been linked with reductions in traffic deaths and those that suggest people often use marijuana instead of alcohol, which is a much riskier drug in terms of violence (including sexual assaults). But they also lean in the same positive direction, as does data showing that legal recreational weed is not associated with rising teen use.

Basically, going after marijuana during an overdose epidemic arguably amounts to one of the dumbest federal government policies in American history. Not only will cutting the pot supply (if that is even achievable—decades of the War on Drugs suggest otherwise) be likely to drive more, rather than fewer, people towards opioids, but any money spent on doing so cannot be used to fund proven life-saving treatments, like long-term methadone and buprenorphine, which can cut the overdose death rate in half.

Many experts, like Mark Kleiman, professor of public policy at the Marron Institute at New York University, suspect Sessions will not follow through with major new pot enforcement. “What's notable about the Sessions statement is what it doesn't say,” Kleiman told me. “It doesn't mention injunctions. And it doesn't mention using the Narcotic Section of the Criminal Division to prosecute some cases. Looks to me like a bluff—or mostly a bluff. Maybe they'll make a few examples.”

While that might strike fear into investors and people who work in the marijuana business, it’s unlikely to have any long-term impact on the drug policy debate in the country. “This move represents a broken campaign promise by the president,” Tom Angell, author of the indispensable marijuana newsletter and website, Marijuana Moment, told me. “With polls showing that marijuana legalization is way more popular than the president is, this will likely turn out to be a huge political disaster for the administration, as is shown by the crushing bipartisan blowback we're now seeing in Congress. Either way, it's not going to stop even more states from modernizing their cannabis laws.”

Sessions’s move could, however, add at least a temporary roadblock for people seeking a promising alternative treatment for pain and opioid addiction. With nearly 100 people dying from opioid-related overdoses every single day, this is inexcusable.