Does federal drug law override Arizona's voter-approved medical marijuana law, and can the state still issue patient ID cards even if dispensary operations are preempted?

Plain-English summary

After Arizona voters narrowly approved Proposition 203 in 2010, the State sued in federal court asking whether the AMMA was preempted by the federal Controlled Substances Act. The federal court dismissed on ripeness grounds and the question lingered. State employees were caught in a bind: state law required them to administer the AMMA's dispensary licensing system, while federal law continued to treat marijuana distribution as a crime. Thirteen of Arizona's fifteen county attorneys, plus a state legislator, asked the AG to rule on preemption.

Attorney General Horne split the AMMA into two parts. The first part is the dispensary system: AMMA provisions and DHS rules that authorize nonprofit dispensaries to cultivate, sell, and dispense marijuana. Horne concluded those provisions are preempted under obstacle-preemption analysis. He cited two state appellate decisions reaching the same conclusion in similar contexts, the Oregon Supreme Court's Emerald Steel Fabricators (2010) and the California Court of Appeal's Pack v. Superior Court (2011, with review pending in the California Supreme Court). When state law authorizes conduct that federal law prohibits, the state law stands as an obstacle to the federal scheme and cannot survive.

The second part is the patient and caregiver ID card system. The AMMA decriminalizes possession and use of small amounts of marijuana for cardholders. Horne concluded that part is not preempted, because Congress lacks power to force a state to criminalize conduct. A state can leave conduct legal under state law even when federal law forbids it; that is not "authorization" in the obstacle-preemption sense, just a refusal to add state criminal liability on top of federal liability. The card identifies someone whose conduct has been decriminalized; it does not authorize them to violate federal law. To the extent that an ID card on its face purports to authorize cultivation or other federally illegal conduct, that authorization is preempted, but the basic registry function is fine.

The opinion left a separate hard question unresolved: whether state employees who administer the AMMA's licensing functions can themselves be federally prosecuted under the CSA. Horne declined to answer that, noting it lay in DOJ discretion. He cited a February 2012 letter from the Acting U.S. Attorney for Arizona stating that AMMA compliance "will not provide a safe harbor or immunity from federal prosecution" for those involved in cultivation and distribution, and that state employees who carry out AMMA functions "are not immune from liability under the CSA."

Currency note

This opinion was issued in 2012. Subsequent statutory amendments, court decisions, or later AG opinions may have changed the analysis. Treat this page as historical context, not current legal advice. Verify current law before relying on any specific rule, deadline, or remedy mentioned here. The opinion's preemption analysis was contested from the start; later state-court rulings, including by Arizona's own courts, came out differently in some respects, and the federal political landscape has shifted dramatically (Cole Memo, Rohrabacher-Farr/Joyce amendment, multiple state-legalization waves, and Arizona's 2020 adult-use vote). The decriminalization-versus-authorization distinction the AG drew is still a useful framework for thinking about state cannabis regulation.

Background and statutory framework

The Supremacy Clause makes federal law the supreme law of the land and gives Congress preemption power. There are several types of preemption: express, field, and conflict (which itself splits into impossibility and obstacle preemption). The AG's analysis was an obstacle-preemption analysis: state law that purports to authorize conduct federal law forbids "stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress." Mich. Canners is the canonical statement.

The Controlled Substances Act lists marijuana as Schedule I, meaning Congress has determined it has no accepted medical use and a high abuse potential. Gonzales v. Raich (2005) confirmed that the CSA reaches even purely intrastate medical-marijuana cultivation under the Commerce Clause. United States v. Oakland Cannabis Buyers' Coop. (2001) ruled out a medical-necessity defense to federal prosecution.

The decriminalization-versus-authorization split is the heart of the opinion's reasoning. The Supreme Court has long held that Congress cannot commandeer state legislatures to criminalize conduct (the anti-commandeering line, Printz v. United States and others), and Emerald Steel applied that principle directly: a state that simply chooses not to criminalize medical marijuana possession does not "authorize" anything in the obstacle-preemption sense. The dispensary licensing system, on the other hand, does affirmatively authorize cultivation and distribution, and that affirmative authorization is what runs afoul of the CSA in the AG's analysis.

Common questions

Q: If the dispensary system was preempted in 2012, why did dispensaries continue operating?
A: AG opinions are persuasive but not binding. State courts and federal courts in Arizona did not adopt the AG's preemption analysis as the controlling rule, and the political environment shifted toward tolerance of state medical-marijuana programs. By 2020, Arizona voters approved Proposition 207 for adult-use cannabis, which made the question largely moot for state-law purposes.

Q: Could a federal prosecutor have shut down all Arizona dispensaries based on this opinion?
A: The opinion did not affect federal enforcement discretion at all. Federal prosecutors can already enforce the CSA regardless of state law. The opinion's significance was its conclusion that state agencies could not lawfully administer the dispensary licensing system, not that dispensaries themselves became newly illegal.

Q: Does this preemption analysis still apply to adult-use cannabis under Proposition 207?
A: The same federal-preemption arguments could be made, and several states have litigated similar issues. The Cole Memorandum (2013) and the Rohrabacher-Farr/Joyce amendment have changed the federal enforcement posture, but they do not formally change the underlying preemption analysis. Verify current federal posture and current AG guidance before acting.

Q: Are state employees personally exposed to federal prosecution for administering the AMMA or Prop 207?
A: This opinion explicitly declined to answer, calling it a matter of DOJ discretion. The acting U.S. Attorney's February 2012 letter took the position that state employees were not immune. As a practical matter, no state employee has been prosecuted federally for AMMA or Prop 207 administration, but the formal legal exposure has not been resolved.

Citations and references

Statutes and constitutional provisions:
- U.S. Const. art. VI, cl. 2 (Supremacy Clause)
- 21 U.S.C. § 801 et seq. (Controlled Substances Act)
- A.R.S. § 36-2801 (AMMA definitions)
- A.R.S. § 36-2811 (decriminalization)

Cases:
- Gonzales v. Raich, 545 U.S. 1 (2005), CSA reaches intrastate medical use
- United States v. Oakland Cannabis Buyers' Coop., 532 U.S. 483 (2001), no medical-necessity defense
- Emerald Steel Fabricators, Inc. v. Bureau of Labor & Indus., 230 P.3d 518 (Or. 2010), obstacle preemption applied
- Pack v. Superior Court, 132 Cal. Rptr. 3d 633 (App. 2011), preemption of dispensary licensing

Source

• Landing page: https://www.azag.gov/opinions/i12-001-r12-008
• Original PDF: https://www.azag.gov/sites/default/files/2025-06/I12-001.pdf

Original opinion text

To:

The Honorable John Kavanaugh,

State Representative

Sheila Polk,

Yavapai County Attorney

Ken Angle,

Graham County Attorney

Brad Carlyon,

Navajo County Attorney

Daisy Flores,

Gila County Attorney

Barbara LaWall,

Pima County Attorney

Bill Montgomery,

Maricopa County Attorney

Ed Rheinheimer,

Cochise County Attorney

George Silva,

Santa Cruz County Attorney

Jon R. Smith,

Yuma County Attorney

Matt Smith,

Mohave County Attorney

James P. Walsh,

Pinal County Attorney

Michael Whiting,

Apache County Attorney

Derek Rapier,

Greenlee County Attorney

Question Presented

The following question has been presented to this Office by a member of the Legislature and thirteen of Arizona’s fifteen county attorneys: Is the Arizona Medical Marijuana Act (“the AMMA”) preempted by the federal Controlled Substances Act (“the CSA”)?

Summary Answer

Yes, in part. The Supremacy Clause of the United States Constitution provides that federal law “shall be the supreme law of the land . . . anything in the constitution or laws of any state to the contrary notwithstanding.” U.S. Const. art. VI, cl. 2. Because of federal prohibitions, those AMMA provisions and related rules that authorize any cultivating, selling, and dispensing of marijuana are preempted. However, the AMMA provisions and related rules that pertain to the issuance of registry identification cards for patients and caregivers are not preempted because they merely serve to identify those individuals for whom the possession or use of marijuana has been decriminalized under state law and, therefore, are not authorizations to violate federal law.

Background

The AMMA was passed narrowly by voters in 2010 as Proposition 203. The purpose of the proposition, as explained by the Arizona Legislative Council’s ballot measure analysis provided to all voters, was to “allow a ‘qualifying patient’ who has a ‘debilitating medical condition’ to obtain an ‘allowable amount of marijuana’ from a ‘nonprofit medical marijuana dispensary’ and to possess and use the marijuana to treat or alleviate the debilitating medical condition or symptoms associated with the condition.” Ariz. Sec’y of State, Ariz. Ballot Prop. Guide, Gen. Election—Nov. 2, 2010, at 83 (quoting Ariz. Rev. Stat. (“A.R.S.”) § 36-2801), available at azsos.gov/election/2010/info/PubPamphlet/english/prop203.pdf. In order to facilitate its implementation, the AMMA requires that “[t]he Arizona Department of Health Services [“DHS”] . . . adopt and enforce a regulatory system for the distribution of marijuana for medical use, including a system for approving, renewing and revoking the registration of qualifying patients, designated caregivers, nonprofit dispensaries and dispensary agents.” Id.; see also A.R.S. § 36-2803. After the Act took effect, DHS promulgated rules related to its implementation. See Ariz. Admin. Code §§ R9-17-101 to R9-17-323 (2011).

Following the AMMA’s passage, the State brought questions relating to preemption to two different courts. In Arizona v. United States, No. 2:11-cv-01072-SRB (D. Ariz. 2011), the State expressed concern that while the “employees and officers of the State of Arizona have a mandatory duty to implement” the AMMA (subject to a legal action in mandamus), state officials “risk prosecution and penalties under federal criminal statutes if they faithfully comply with Arizona law.” See Compl. at 15, ¶ 81. The Complaint sought declaratory relief and asked the federal court to determine whether the AMMA was preempted by federal law or whether implementation of the AMMA was subject to a “safe harbor” by virtue of certain actions of the federal government. See generally id. The district court judge, however, concluded that the State had not met “the constitutional or prudential components of ripeness” and dismissed its complaint. Order, Arizona v. United States, No. 2:11-cv-01072-SRB at 10 (D. Ariz. January 4, 2012). Similar issues were raised in a mandamus action against DHS in Superior Court for Maricopa County. See Minute Entry, Compassion First LLC v. State, No CV 2011-011290 at 5 (January 17, 2012). In that case the superior court judge recognized “the State’s dilemma” explaining that “it is caught between the proverbial rock and hard place, between the AMMA and the CSA.” Id. Nevertheless, the court declined to “determine issues of preemption and federal criminal liability,” instead concluding that the “sole issue before [it was] whether the State has discretion to put the implementation of the AMMA on hold while it” sought relief on those issues in federal court.(1) Id.

Analysis

The Supremacy Clause of the United States Constitution declares that the “Constitution, and the Laws of the United States . . . shall be the supreme law of the land . . . anything in the constitution or laws of any state to the contrary notwithstanding.” U.S. Const. art. VI, cl. 2. “Under this principle, Congress has the power to preempt state law.” Arizona v. United States, 132 S. Ct. 2492, 2500 (2012). In passing the CSA, Congress recognized that “[t]he illegal importation, manufacture, distribution, and possession and improper use of controlled substances have a substantial and detrimental effect on the health and general welfare of the American people.” 21 U.S.C. § 801(2). Furthermore, Congress found that “[c]ontrolled substances manufactured and distributed intrastate cannot be differentiated from controlled substances manufactured and distributed interstate” and concluded that “it is not feasible to distinguish, in terms of controls, between controlled substances manufactured and distributed interstate and controlled substances manufactured and distributed intrastate.” Id. § 801(5). “The CSA designates marijuana as contraband for any purpose; in fact, by characterizing marijuana as a Schedule I drug [under the Act], Congress expressly found that the drug has no acceptable medical uses.” Gonzales v. Raich, 545 U.S. 1, 27 (2005). Consequently, although the CSA “expressly contemplates that many drugs ‘have a useful and legitimate medical purpose and are necessary to maintain the health and general welfare of the American people’ . . . it includes no exception at all for any medical use of marijuana.” United States v. Oakland Cannabis Buyers’ Coop., 532 U.S. 483, 493 (2001) (internal citation omitted) (rejecting medical necessity argument as defense to criminal prosecution).

This issue has been ruled on in two (2010, 2011) appellate court cases, one in California and one in Oregon. The legal analysis in these cases controls this opinion. See Mich. Op. Att’y Gen. No. 7262, 2011 WL 5848600, at *4 n.11 (2011) (concluding that the recent Oregon and California decisions render prior decisions related to medical marijuana “of questionable value”).

First, the Oregon Supreme Court concluded, in analyzing Oregon’s similar medical marijuana program, that those provisions of the Oregon law that authorized “a use that federal law prohibits stand[] as an obstacle to the implementation and execution of the full purposes and objectives of the [CSA].” Emerald Steel Fabricators, Inc. v. Bureau of Labor & Indus., 230 P.3d 518, 529 (Or. 2010). That court explained that under U.S. Supreme Court precedent, where a state law authorizes “conduct that the federal Act forbids, ‘it stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress.’” Id. (quoting Mich. Canners & Freezers Ass’n v. Agric. Mktg. & Bargaining Bd., 467 U.S. 461, 478 (1984)).

Similarly, the California Court of Appeals has held that where an ordinance creates an application process that permits it to operate a medical marijuana collective, the ordinance’s authorization “stands as an obstacle to the accomplishment of [the] purpose [of the CSA].” Pack v. Superior Court, 132 Cal. Rptr. 3d 633, 651 (App. 2011), rev. granted, 268 P.3d 1063 (2012).(2)

In contrast, a state’s decision concerning the decriminalization of certain conduct stands on a different footing because “[w]hen an act is prohibited by federal law, but neither prohibited nor authorized by state law, there is no obstacle preemption.” Id.;accord Emerald Steel, 230 P.3d at 530 (“Congress lacks authority to require states to criminalize conduct that the states choose to leave unregulated, no matter how explicitly Congress directs the states to do so.”). Here, the AMMA decriminalizes the possession and use of marijuana of up to 2.5 ounces for those individuals (patients and caregivers) who have been issued certain identification cards. A.R.S. § 36-2811. But the language of the statute does not authorize anything. This provision, by the terms of the statute, is not preempted because it is beyond Congress’s power to dictate the parameters of state criminal conduct. However, to the extent that an identification card purports to authorize an individual to cultivate marijuana or otherwise violate federal law, such language is preempted.(3)

Conclusion

In light of the legal principles outlined above, and the continuing concerns raised by the chief law enforcement officers of thirteen of Arizona’s fifteen counties throughout the state, I must issue this opinion concluding that those provisions of the AMMA and related rules authorizing any cultivating, selling, and dispensing of marijuana are preempted. However, the AMMA provisions and related rules that pertain to the issuance of registry identification cards for patients and caregivers are not preempted because they merely serve to identify those individuals for whom the possession or use of marijuana has been decriminalized under state law and, therefore, are not authorizations to violate federal law.

Thomas C. Horne

Attorney General

Subsequent litigation in other matters has raised similar issues. See, e.g., State v. Okun, No. 1 CA-CV 12-0094 (App. Feb. 9, 2012), docket available at apps.supremecourt.az.gov/aacc/appella/1CA%5CCV%5CCV120094.PDF; Answer of County Defendants, White Mountain Health Cntr., Inc. v. Cnty. of Maricopa, CV2012-053585 (Ariz. Sup. Ct. June 19, 2012).

In addition, “Congress continues to support the existing Federal legal process for determining the safety and efficacy of drugs and opposes efforts to circumvent this process by legalizing marijuana, and other Schedule I drugs, for medicinal use without valid scientific evidence and the approval of the Food and Drug Administration.” Act of Oct. 21, 1998, Pub. L. No. 105-277, Div. F., 112 Stat. 2681-2761.

You have also asked whether state and other government employees face federal criminal sanctions for administering, implementing, or complying with the AMMA. I am unable to answer this question as it lies in the discretion of the U.S. Department of Justice. Under federal law it appears that state and other government employees could be subject to prosecution for actions required by the AMMA. For example, the most recent statement of the then-Acting U.S. Attorney for Arizona stated that “[c]ompliance with the AMMA and Arizona regulations will not provide a safe harbor or immunity from federal prosecution for anyone involved in the cultivation and distribution of marijuana . . . [a]s such, state employees who conduct activities authorized by the AMMA are not immune from liability under the CSA.” Letter of Acting U.S. Attorney Ann Birmingham Scheel to Governor Janice K. Brewer (Feb. 16, 2012).