On Jan. 4, Attorney General Jeff Sessions rang in the new year by overturning Obama-era Department of Justice (DOJ) guidelines that effectively allowed states to develop legal cannabis programs without fear of federal interference.

Spelled out in the Cole memo, named for Deputy Attorney General James M. Cole, as long as cannabis growers, distributors and users complied with state laws and did not engage in such activities as selling to minors or trafficking across state lines, the DOJ would not prosecute them for violating federal law, and states would be allowed to implement the wishes of voters who elected to legalize cannabis for medical or adult-use purposes. The Cole memo was a pragmatic policy that worked.

Now Sessions wants to bring about a wide-scale crackdown on the legal cannabis industry. But such a crackdown is unlikely in practice since it means that U.S. attorneys would have to divert resources from other enforcement priorities and need the cooperation of local and state authorities who may oppose federal intervention.

And such opposition is almost certain; congressional Republicans and Democrats from states in which cannabis is legal quickly issued statements in defiance of the new guidelines, and governors of many of these states have said they will challenge enforcement efforts. Several U.S. attorneys have already said they will continue not to prosecute individuals operating within the boundaries of state laws.

The negative reactions seen so far mean Sessions will probably not get the enforcement he wants. Instead, because the new guidelines leave discretion to individual U.S. attorneys, it is more likely that federal enforcement will vary by state and region, further exacerbating the patchwork-like nature of cannabis laws across the country.

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Sessions seems to operate on the assumption that heavier enforcement of prohibition would reduce cannabis use. But history demonstrates that even the most aggressive enforcement of federal law would not stifle cannabis use or sales; rather, it would drive them underground where criminal enterprises would reap the profits, tax-free, and where consumers would face greater threats to their health due to lack of regulation.

Sessions claims that his decision is driven by concern for the dangers that cannabis poses to society, but this fear is not supported by any legitimate evidence. Survey data indicate that cannabis legalization has not resulted in increased use among teenagers; in Colorado teen use is lower now than it was prior to adult-use legalization. Several studies attempting to show a relationship between legalized cannabis and increased crime rates have found none. To the contrary, the evidence suggests that cannabis prohibition causes far greater harm to society than cannabis itself.

Prohibition states spend hundreds of millions of dollars each year on enforcement efforts that do little to reduce cannabis use and disproportionately impact the poor and people of color, saddling thousands with a criminal record that makes it difficult if not impossible for them to obtain employment and access housing and education services.

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If Sessions wants to protect society, he needs an improved understanding of what truly threatens it. In the face of the biggest drug crisis today, the opioid epidemic, cannabis could offer a partial solution. States in which medical use of cannabis is legal have roughly 1,800 fewer painkiller doses prescribed per physician annually than other states, and several studies have found an association between access to legal medical cannabis and lower rates of opioid use and overdose.

Protections for medical cannabis businesses and patients currently hang by a thread known as the Rohrabacher-Farr amendment, which prevents the DOJ from using funds to prosecute them in the 29 states and the District of Columbia where medical cannabis is legal. That number is 45 if you count states like Texas that have more restrictive low-tetrahydrocannabinol (THC)-medical cannabis programs. (THC is the chemical compound in cannabis responsible for a euphoric high).

If Sessions has his way, Congress will allow that amendment to expire Jan. 19, but fierce opposition could push Congress to renew the protections for medical cannabis states and the roughly 2.3 million patients who rely on the drug for pain relief.

In fact, Sessions' approach may have the unintended effect of speeding up cannabis prohibition's demise. Between the Rohrabacher-Farr amendment and the Cole memo, Congress had enough political cover in the past to allow it to sidestep the question of repeal. By throwing the issue into the spotlight, Sessions could push Congress to pick a side, and it could side with the 64 percent of Americans and 51 percent of Republicans who favor cannabis legalization.

Given the negative consequences that would come from greater enforcement of cannabis prohibition, there is reason not to enforce these laws, but to change them. Sessions' directive could be the impetus to repeal a law that should have never existed in the first place. That is not what Sessions wants, but that may be what Sessions gets.

Editor's note: Much has already been written on this topic; more in-depth analysis of Sessions' decision can be accessed here, here and here. For more information on the impact of cannabis reform, check out the Baker Institute's issue brief, "Marijuana Reform: Fears and Facts."

Dr. Katharine Neill Harris is the Alfred C. Glassell, III, Fellow in Drug Policy at the Baker Institute at Rice University.

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