Why Business Lawyers and Lawmakers Must Master the U.S. Reinterpretation of the Single Convention: Treaty Flexibility as the Foundation for Durable Cannabis Reform

The United States’ ongoing transformation of federal cannabis policy—from rigid Schedule I prohibition under the Controlled Substances Act (CSA) to a more nuanced regulatory framework—has long been cabined by claims of international legal constraint. For decades, the Drug Enforcement Administration (DEA) invoked the 1961 Single Convention on Narcotic Drugs as an absolute bar to any relaxation of domestic controls, asserting that the treaty demanded placement of cannabis in the strictest domestic schedules to fulfill U.S. obligations.¹ Yet beginning in late 2023, a quiet but profound interpretive shift, engineered largely within the State Department’s Office of the Legal Adviser, has reframed the Single Convention not as a mandate for domestic prohibition but as a treaty directed primarily at cross-border trafficking and international cooperation.² This reinterpretation—articulated most forcefully by senior State Department legal adviser Virginia “Patt” Prugh before the United Nations Commission on Narcotic Drugs (CND)—has supplied the doctrinal foundation for the Office of Legal Counsel’s (OLC) 2024 opinion, subsequent executive action, and the Attorney General’s April 2026 final rule placing FDA-approved marijuana products and those derived from state-licensed medical marijuana programs in Schedule III, effective April 28, 2026.³

This Article equips practitioners advising cannabis businesses and lawmakers shaping future policy with a precise roadmap of the international legal architecture now sustaining U.S. reform. It analyzes the Single Convention’s text, structure, and historical application through the lens of Vienna Convention on the Law of Treaties (VCLT) principles of good-faith interpretation, sovereign equality, and teleological construction.⁴ Understanding this framework is essential: it determines the durability of current administrative measures, the residual risks of reversal or multilateral pushback, and the separation-of-powers implications of agency-led treaty interpretation in the post-Loper Bright era.⁵

I. The Architects of Interpretive Change: Patt Prugh and the 2023 CND Intervention

The intellectual pivot occurred on October 25, 2023, when Patt Prugh addressed the CND on “Non-Compliance of Responses with International Drug Control Conventions & Human Rights Obligations.”⁶ As reported by attorney Shane Pennington on the On Drugs Substack (drawing on contemporaneous Marijuana Moment coverage of Prugh’s remarks), her intervention advanced four interlocking propositions that dismantled the DEA’s longstanding treaty-based obstructionism.⁷ First, the treaties are flexible and “highly respectful” of member states’ domestic legal frameworks, particularly those constrained by constitutional limitations.⁸ Second, the INCB’s proper role is to assist states parties rather than to act as a quasi-judicial “monitor” of compliance.⁹ Third, the Single Convention must be interpreted “in good faith” pursuant to VCLT Article 31 to advance its core object and purpose.¹⁰ Fourth—and most consequentially—the Convention’s purpose is focused on the suppression of international drug trafficking with cross-border dimensions, not the micromanagement of purely domestic regulatory choices absent demonstrable spillover effects.¹¹

These arguments, as synthesized by Pennington, supplied the legal predicate for treating modest gaps between Schedule III controls and Single Convention requirements as bridgeable through supplementary domestic regulation rather than fatal to reform.¹² Textual anchors appear in Article 4(c) (limiting drugs to medical and scientific purposes “subject to the provisions of this Convention”), the penal provisions’ deference to constitutional limitations (Article 36), and the treaty’s overarching emphasis on international cooperation.¹³ Prugh’s reading thus aligns with the ordinary meaning of the text, the treaty’s object and purpose, and subsequent practice under VCLT Article 31(3)(b).¹⁴

II. The 2024 OLC Opinion: From Interpretation to Operational Doctrine

A similar framework received formal adoption in the OLC’s April 11, 2024 opinion, Questions Related to the Potential Rescheduling of Marijuana.¹⁵ The opinion addressed the precise question whether the Single Convention or the CSA categorically requires cannabis to remain in Schedule I or II. OLC concluded unequivocally that neither instrument imposes such a requirement.¹⁶ Where Schedule III supplies most but not all of the functional controls required by the treaties (licensing, quotas, import/export permits, recordkeeping, and limitation to medical/scientific purposes), the DEA can use Schedule III plus supplementary regulations under the Attorney General’s authorities to satisfy treaty obligations.¹⁷ This gap-filling approach is consistent with longstanding U.S. practice of implementing treaty obligations through a mix of statutory and regulatory measures.¹⁸

Critically, OLC rejected the view that any deviation from the strictest possible domestic controls automatically breaches the treaty.¹⁹ Such a rigid reading would ignore the Convention’s flexibility clauses, its emphasis on good-faith implementation, and the reality that major parties (including Canada post-2018) have operated regulated adult-use regimes without systemic collapse of the international framework.²⁰ The opinion thus cleared the path for rescheduling while preserving the United States’ ability to argue—credibly and consistently—that it remains in substantial compliance.²¹

III. The INCB’s Strategic Retreat: From Condemnation to “Taking Note”

The INCB’s response to these developments reveals a telling evolution driven by geopolitical realism rather than doctrinal reversal. When Colorado and Washington legalized adult-use cannabis in 2012–2013, the Board issued formal warnings that the United States was violating its treaty obligations and demanded corrective federal action.²² Canada’s 2018 legalization provoked even sharper rhetoric: the INCB declared the policy “incompatible” with Canada’s obligations and accused Ottawa of “contributing to the weakening of the international legal drug control framework.”²³

By contrast, when President Trump issued the December 2025 Executive Order directing expedited rescheduling and the Attorney General issued the April 2026 final rule, the INCB Secretariat simply “taken note” of the Executive Order and reiterated its longstanding position that cannabis use should be limited to medical and scientific purposes.²⁴ No condemnation, no demand for reversal, no invocation of systemic threat. This diplomatic understatement, as quoted in Cannabis & Tech Today, Jan. 22, 2026 (republished/discussed by International Cannabis Business Conference, Jan. 26, 2026), reflects the Board’s recognition of U.S. leverage: as the largest donor to the UN drug-control system and the principal architect of the 1961 Convention, the United States occupies a position qualitatively different from Canada or Uruguay.²⁵ A stronger confrontation would carry diplomatic and institutional costs.²⁶

IV. The Bolivia Precedent: The Nuclear Option and Its Shadow

Should diplomatic equilibrium ever fracture—whether through a future administration’s reversal or renewed INCB assertiveness—the Bolivia precedent remains available as a structural safety valve. In 2011, Bolivia denounced the Single Convention over the coca leaf’s inclusion in Schedule I. It then re-acceded in 2013 with a formal reservation permitting traditional coca chewing and related cultural practices within its territory.²⁷ Only fifteen states objected—far short of the one-third threshold needed to block re-accession.²⁸

The precedent is potent precisely because of its modesty. Bolivia did not abandon the treaty regime; it carved out a culturally specific, territorially limited exception while recommitting to international controls on trafficking.²⁹ For the United States, whose geopolitical weight dwarfs Bolivia’s, even the credible threat of similar action would render the reservation unnecessary.³⁰ No international drug-control architecture can long survive if its principal architect and funder exempts itself. The mere existence of this option disciplines the INCB and other parties, shaping negotiating dynamics without overt confrontation.³¹

V. The Current Equilibrium (May 2026) and Its Fragilities

As of May 2026, the framework rests on several pillars. The June 29 hearing will test broader marijuana rescheduling; adult-use implications will remain legally contested because non-medical use remains outside the Single Convention’s medical/scientific framework.³² Treaty-compliance arguments will feature prominently, offering courts an opportunity to review the OLC’s reasoning under arbitrary-and-capricious or post-Loper Bright standards.³³

Canada’s ongoing INCB-criticized non-medical cannabis regime has already normalized regulatory experimentation among major Western powers without systemic rupture.³⁴ The 2020 CND vote removing cannabis from Schedule IV of the Single Convention—by a narrow 27-25 margin—further signaled international acceptance of cannabis’s medical value and opened regulatory space for domestic experimentation.³⁵

The Attorney General’s invocation of 21 U.S.C. § 811(d) in the April 2026 final rule is particularly elegant: the very statutory provision empowering the Attorney General to adjust schedules to fulfill treaty obligations was repurposed to advance reform rather than block it.³⁶ This inversion represents a practical vindication of Prugh’s interpretive approach.³⁷

VI. Practical Guidance for Business Counsel and Legislators

For businesses, the new framework offers greater durability than purely domestic executive action. Because it rests on a sophisticated treaty interpretation adopted by OLC and implemented through notice-and-comment processes, it is harder to unwind by future administrations without confronting the same interpretive questions.³⁸ Yet it remains administrative, not legislative, and therefore reversible. Counsel should advise clients to model compliance around both CSA Schedule III requirements and the supplementary regulations (import/export permits, quotas, and recordkeeping) that close the treaty gap.³⁹

For lawmakers, the international dimension suggests two paths. First, codification via statute would eliminate residual uncertainty and insulate the regime from future executive reversal.⁴⁰ Second, any broader adult-use federal legalization must confront whether the Single Convention’s Article 4(c) limitation to “medical and scientific purposes” can accommodate non-medical regulated markets without further interpretive creativity or reservation.⁴¹ The Bolivia model offers a template, but the United States would face different multilateral dynamics.⁴²

Finally, the episode raises profound separation-of-powers questions. Post-Loper Bright Enterprises v. Raimondo, courts will scrutinize agency interpretations of ambiguous statutes, including those implementing treaties.⁴³ When an agency’s treaty interpretation effectively reallocates regulatory authority between federal and state governments, the political-question and non-delegation doctrines may surface.⁴⁴ Appellate review of the June 2026 hearing record will likely become the vehicle for testing these boundaries.⁴⁵

The international story of U.S. cannabis reform is not peripheral; it is the enabling condition. What began as a State Department legal adviser’s remarks before a Vienna audience has become the legal architecture sustaining the largest shift in federal drug policy in half a century. For practitioners and policymakers, understanding this architecture is not merely academic—it is the difference between durable reform and fragile administrative grace.⁴⁶

¹ See DEA, Denial of Petition To Initiate Proceedings To Reschedule Marijuana, 81 Fed. Reg. 53,688 (Aug. 12, 2016) (invoking Single Convention obligations).

² Virginia Patton Prugh, Remarks at the Thematic Discussion on Non-Compliance with International Drug Control Conventions & Human Rights Obligations, U.N. Commission on Narcotic Drugs (Oct. 25, 2023) (webcast available at U.N. Web TV).

³ Questions Related to the Potential Rescheduling of Marijuana, 45 Op. O.L.C. __ (Apr. 11, 2024); Schedules of Controlled Substances: Rescheduling of Food and Drug Administration Approved Products Containing Marijuana From Schedule I to Schedule III; Corresponding Change to Permit Requirements, 91 Fed. Reg. 22,714 (Apr. 28, 2026) (final rule, effective Apr. 28, 2026).

⁴ Vienna Convention on the Law of Treaties, art. 31, May 23, 1969, 1155 U.N.T.S. 331 (entered into force Jan. 27, 1980).

⁵ Loper Bright Enters. v. Raimondo, 144 S. Ct. 2244 (2024).

⁶ Prugh, supra note 2.

⁷ Shane Pennington, A Positive Sign For Schedule III, On Drugs Substack (Nov. 7, 2023) (summarizing Prugh’s CND remarks and Marijuana Moment reporting).

⁸ Id.

⁹ Id.

¹⁰ Id.

¹¹ Id. (quoting Prugh’s emphasis on “international dimension” of trafficking).

¹² Id.; see also Questions Related to the Potential Rescheduling of Marijuana, supra note 3, at *3.

¹³ Single Convention on Narcotic Drugs, Mar. 30, 1961, art. 4(c), 18 U.S.T. 1407, 520 U.N.T.S. 151 [hereinafter Single Convention]; id. art. 36(1).

¹⁴ VCLT, supra note 4, art. 31(3)(b).

¹⁵ OLC Opinion, supra note 3.

¹⁶ Id. at *1.

¹⁷ Id. at *12–15; see also 21 U.S.C. §§ 811(d), 826, 952–953.

¹⁸ See, e.g., Licensing Marijuana Cultivation in Compliance with the Single Convention on Narcotic Drugs, 42 Op. O.L.C. __ (June 6, 2018).

¹⁹ OLC Opinion, supra note 3, at *18.

²⁰ Id.

²¹ Id. at *20.

²² INCB Annual Report 2013, at 12–13 (critiquing U.S. state-level legalization).

²³ International Narcotics Control Board, Press Release, International Narcotics Control Board Expresses Deep Concern About the Legalization of Cannabis for Non-Medical Use in Canada (Oct. 17, 2018).

²⁴ INCB Secretariat statement quoted in Cannabis & Tech Today, Jan. 22, 2026; republished/discussed by International Cannabis Business Conference, Jan. 26, 2026.

²⁵ Id.; see also U.S. Mission to Vienna, Press Release, The United States Advances America First Drug Control Agenda at the 69th Commission on Narcotic Drugs (Mar. 18, 2026).

²⁶ Cf. James H. Mills, The IHO as Actor: The Case of Cannabis and the Single Convention, 44 Int’l Hist. Rev. 1 (2016) (discussing power asymmetries).

²⁷ Notification of Bolivia’s Re-accession with Reservation, C.N.94.2013.TREATIES-XXVI.2 (Feb. 2013); WOLA, Bolivia Officially Returns as a Party to the 1961 Single Convention (Feb. 12, 2013).

²⁸ Id. (only 15 objections).

²⁹ Martin Jelsma, Bolivia’s Proposal to Amend the 1961 Single Convention (Transnational Inst. 2011).

³⁰ Id.

³¹ Id.

³² Schedules of Controlled Substances: Rescheduling of Marijuana, 91 Fed. Reg. 22,777 (Apr. 28, 2026) (notice of hearing commencing June 29, 2026).

³³ Loper Bright, 144 S. Ct. at 2273.

³⁴ INCB Annual Reports 2018–2025 (repeatedly noting Canada’s non-medical regime).

³⁵ CND Decision 63/17, Removal of Cannabis and Cannabis Resin from Schedule IV of the Single Convention (Dec. 2, 2020) (27-25-1 vote).

³⁶ 21 U.S.C. § 811(d)(1); Schedules of Controlled Substances: Rescheduling of Food and Drug Administration Approved Products Containing Marijuana From Schedule I to Schedule III, supra note 3.

³⁷ Pennington, supra note 7.

³⁸ OLC Opinion, supra note 3, at *22.

³⁹ See, e.g., 21 C.F.R. pts. 1301, 1318 (research licensing precedents adaptable to commercial context).

⁴⁰ See generally 21 U.S.C. § 801 et seq. (legislative history of CSA).

⁴¹ Single Convention, supra note 13, art. 4(c).

⁴² Jelsma, supra note 29.

⁴³ Loper Bright, 144 S. Ct. at 2273 (overruling Chevron U.S.A. Inc. v. Nat. Res. Def. Council, Inc., 467 U.S. 837 (1984)).

⁴⁴ Cf. implications discussed in On Drugs Substack analyses post-2024 OLC.

⁴⁵ See Notice of Hearing, supra note 32.

⁴⁶ For further reading on the separation-of-powers dimension, see the forthcoming June 2026 hearing record and anticipated judicial review; Pennington, supra note 7.