This Lead Up to Legalization blog series will cover California’s foray into legalized recreational marijuana. We will cover issues leading up to our state’s January 2018 implementation, including the structure of Proposition 64, marijuana’s classification under the Controlled Substances Act, and many other issues that arise during the state’s transition.

At the time of this post, eight states have legalized marijuana for recreational adult use, and 29 states have some form of legalized medical marijuana. At the same time, cannabis remains a Schedule I drug under the federal Controlled Substances Act, meaning that any use or possession of the drug is illegal under federal law. How then can states legalize any form of marijuana, whether recreational or medical, without facing sanctions from the federal government?

The answer largely lies with two memos written by attorneys at the United States Department of Justice during the Obama administration. The memos provided states with the basic guidelines for legalizing marijuana. Essentially, if the states met the suggested elements in the memos, federal prosecutors were encouraged to direct their attention elsewhere. The first memo, written by Deputy Attorney General David Ogden in 2009, provided guidelines for states that had legalized marijuana for medical purposes. Ogden notes that the Justice Department’s main priorities focus on “the disruption of illegal drug manufacturing and trafficking networks,” but clarifies, “As a general matter, pursuit of these priorities should not focus federal resources…on individuals whose actions are in clear and unambiguous compliance with existing state laws providing for the medical use of marijuana.” Ogden provides several factors that would raise a red flag for federal prosecutors and invite prosecution, including: sales to minors, violence, and unlawful use of firearms associated with medical marijuana sales.

In 2013, Deputy Attorney General James Cole published a similar memo, this time regarding both medical and recreational marijuana. Like Ogden’s memo, the “Cole memo,” as it is commonly referenced, lists eight issues that states should account for in their marijuana regulations, or else risk triggering federal prosecution. These include, among others: preventing the distribution of marijuana to minors, diversion of marijuana to states that have not legalized the substance, and use or possession of marijuana on federal property. Cole sets up a similar federal-state balance as Ogden did, writing that states with strong marijuana regulatory systems that prevent the issues listed out in his memo are “less likely to threaten the federal priorities,” and therefore less likely to trigger federal prosecution.

Neither the Cole nor the Ogden memos constitute a guarantee or absolute shield against federal enforcement of the Controlled Substances Act. The memos themselves even contain such disclaimers.For example, the last sentence of the Cole memo reads, “Finally, nothing herein precludes investigation or prosecution, even in the absence of any one of the factors listed above, in particular circumstances where investigation and prosecution otherwise serves an important federal interest.” Even so, federal resources are currently unlikely to be used to prosecute individuals for personal marijuana use in legalized states.

Thus far into the current administration, the Justice Department has abided by these memos and allowed states to set up marijuana regulatory structures in compliance with the Cole and Ogden memos. However, the memos do not technically have the force of law. A new memo from the Trump administration’s Justice Department could reinstate federal prosecution without regard to the Cole and Ogden memos.

President Trump has made conflicting statements on his stance regarding state-legal marijuana. Thus, the future remains uncertain for these states.

The next post in this series will go over the federal Controlled Substances Act and how cannabis fits into that regime.

Kendall Fisher is Editor in Chief of the University of the Pacific Law Review and law student student at McGeorge School of Law in Sacramento.