The League of Nations and Cannabis
How a 1925 League of Nations treaty pulled cannabis into international drug control — and why the evidence behind it was so thin.
Cannabis entered international drug control almost by accident. At a 1924–25 Geneva conference about opium, Egypt's delegate insisted that hashish caused 30–60% of insanity in Egypt; Cairo's own asylum records attributed under 3% of admissions to it. Delegates did not challenge him, and cannabis was added to the 1925 convention. The popular story that the League studied cannabis and found it dangerous is false: it was a diplomatic decision, and later treaties, including the 1961 Single Convention, built on it.
Timeline
- 1909–1912: The Shanghai Opium Commission and the Hague Opium Convention target opium, morphine and cocaine. Cannabis appears only in a resolution asking governments to "study the question" [1].
- June 1922: South Africa bans the cultivation, sale, possession and use of cannabis [2].
- November 1923: South Africa writes to the League's Opium Advisory Committee calling cannabis "the most important of all the habit-forming drugs" [2].
- November 1924: The Second Opium Conference opens in Geneva. Egypt's delegate proposes adding cannabis [2].
- 19 February 1925: The International Opium Convention is signed, with cannabis ("Indian hemp") under limited international trade control [7].
- 25 September 1928: The convention enters into force.
- 1934–1939: A League sub-committee on cannabis collects national reports; it finishes in December 1939 without new scientific research [2].
- 1961: The UN Single Convention places cannabis in its strictest schedules [8].
- December 2020: The UN Commission on Narcotic Drugs removes cannabis from Schedule IV of the 1961 Convention, following a 2019 WHO recommendation [9].
Background: drug control before 1925
International drug control began with the 1909 Shanghai Opium Commission and the 1912 Hague International Opium Convention, both focused on opium, morphine and cocaine. The Hague Convention mentioned "Indian hemp" only in a resolution asking governments to study the question; it imposed no obligations [1] Strong evidence.
When the League of Nations was established in 1920, it took over drug control through its Advisory Committee on the Traffic in Opium and Other Dangerous Drugs. Its focus remained opiates and cocaine [2] Strong evidence.
How cannabis got onto the agenda
South Africa, which had banned cannabis nationwide in June 1922, asked the League in November 1923 to bring it under international control. The committee circulated a request for information to governments in November 1924, the same month a second opium conference was convened in Geneva [2] Strong evidence.
Egypt had prohibited cannabis decades earlier but struggled with hashish smuggled from Greece, Turkey and the eastern Mediterranean. Historians see its push for international control as an attempt to stop that smuggling [2][3] Strong evidence.
The 1924–25 Geneva conference
Cannabis was not on the official agenda. On the second day of the conference, Egyptian delegate Mohamed El Guindy proposed adding it, calling hashish "at least as harmful as opium, if not more so" [2][5]. Turkey, Greece, South Africa and Brazil supported him; the British delegation objected that it was outside the agenda [2].
In his speech, El Guindy said that "the proportion of cases of insanity caused by the use of hashish varies from 30 to 60 per cent" of all cases in Egypt [2][5] Disputed. A later Egyptian memorandum put the figure at about 70% [2]. The numbers do not survive scrutiny: the 1920–21 annual report of Cairo's Abbasiya Asylum, the larger of Egypt's two mental hospitals, attributed 19 of 715 admissions (2.7%) to hashish — fewer than the 48 attributed to alcohol [2] Strong evidence.
The conference referred the issue to a sub-committee, which recommended complete prohibition; only the United Kingdom, India and the Netherlands opposed it [2]. British India taxed and regulated cannabis rather than banning it, which explains its delegates' resistance [6]. Yet neither the British nor the Indian delegation cited the 1894 Indian Hemp Drugs Commission, which had found moderate use caused no significant physical, mental or moral injury [2][4] Strong evidence.
What the 1925 Convention actually did
The sub-committee's recommendations were heavily diluted by the drafting committee, partly because the United States had walked out of the conference after failing to get stricter opium controls [2]. The final treaty:
- Did prohibit exporting cannabis to countries that banned it, and required import certificates from countries that allowed it [2][7] Strong evidence.
- Did not prohibit production, domestic trade, possession or use, require measures to reduce consumption, or require countries to report production estimates [2] Strong evidence.
In other words, it controlled international trade only. Several European countries went further on their own — for example the UK's Dangerous Drugs Act 1928, the revised Dutch Opium Law of 1928 and Germany's 1929 Opium Law — even though cannabis problems in those countries were minimal [2].
The League's cannabis sub-committee (1934–1939)
In 1934, under pressure from Egypt, the United States and Canada, the Advisory Committee referred cannabis to a sub-committee [2]. It gathered national reports through the late 1930s and completed its work in December 1939. Its conclusions were cautious: it called for more research on cannabis chemistry, addiction and its alleged links to dementia and crime, and noted that in parts of North Africa suppressing cannabis appeared to push users towards heroin [2] Strong evidence. It did not produce original scientific research.
Even at the time, the evidence was questioned. A 1926 New York Times article challenged El Guindy's claims, citing the Indian Hemp Drugs Commission and a US Army study in the Panama Canal Zone [2].
Legacy: from Geneva 1925 to the 1961 Single Convention
When drug control passed from the League to the United Nations after 1946, the 1925 framework carried over. The 1961 Single Convention on Narcotic Drugs consolidated earlier treaties and placed cannabis in Schedules I and IV, its most restrictive categories, without a fresh scientific review [8] Strong evidence. (See also UN drug treaties and cannabis.)
Much of the international legal architecture of cannabis prohibition therefore rests on a 1925 diplomatic decision driven by one country's smuggling problem and unsupported asylum statistics. That is why the 2020 decision to remove cannabis from Schedule IV, following the WHO's 2019 recommendation, was historically significant: it was the first time the system formally revisited that assumption [9] Strong evidence.
Common myths
"The League of Nations studied cannabis and found it dangerous." False. No League-commissioned scientific study underpinned the 1925 decision; the later sub-committee mostly compiled government reports [2] Strong evidence.
"The 1925 Convention banned cannabis." False. It only controlled international trade [2] Strong evidence.
"Hashish caused most insanity in Egypt." Unsupported. Egypt's delegates claimed 30–70%, but Cairo's main asylum attributed 2.7% of admissions to hashish [2] Strong evidence.
"The United States drove cannabis into the 1925 treaty." False. Egypt did; the US delegation had walked out over opium. US pressure mattered later, in the 1930s, under Harry Anslinger [2] Strong evidence.
Sources
- Government International Opium Convention, signed at The Hague, 23 January 1912. League of Nations Treaty Series.
- Reported Bewley-Taylor, D., Blickman, T., & Jelsma, M. (2014). The Rise and Decline of Cannabis Prohibition: The History of Cannabis in the UN Drug Control System and Options for Reform. Transnational Institute / Global Drug Policy Observatory. Chapter 1.
- Peer-reviewed Kozma, L. (2011). Cannabis Prohibition in Egypt, 1880–1939: From Local Ban to League of Nations Diplomacy. Middle Eastern Studies, 47(3), 443–460.
- Government Indian Hemp Drugs Commission. (1894). Report of the Indian Hemp Drugs Commission, 1893–94. Simla: Government Central Printing Office. 7 volumes.
- Government League of Nations. (1924). Records of the Second Opium Conference, Geneva, 17 November 1924 – 19 February 1925, Volume I: Plenary Meetings. League of Nations Publications C.760.M.260.1924.XI.
- Book Mills, J. H. (2003). Cannabis Britannica: Empire, Trade, and Prohibition 1800–1928. Oxford University Press.
- Government International Opium Convention, signed at Geneva, 19 February 1925. League of Nations Treaty Series, Vol. 81, p. 317.
- Government Single Convention on Narcotic Drugs, 1961, as amended by the 1972 Protocol. United Nations.
- Government World Health Organization Expert Committee on Drug Dependence. (2019). Forty-first report: critical review of cannabis and cannabis-related substances. WHO Technical Report Series.
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