Under the supervision of the League of Nation, the nascent international community undertook, in the Interwar years, to promote a normative agenda on individual « bad » behaviours. That agenda focused on the control or prohibition of such traffics as opium and other narcotics, liquor, and obscene publications. The fate of these policies was diverse. Obscene publications remained a minor concern. The League was very wary of dealing with alcohol trade, a very divisive issue among its members ; its only outlet was in the African and Pacific mandates, whose charters highlighted the harmful character of spirits on so-called « backward », indigenous societies, and made it compulsory for the mandatory powers to set up ad hoc policies. Yet the prohibition of the traffic of opium and narcotics developped into a fully-fledged international policy, with special effects in the Middle East. The purpose of the paper is to question the transformation of a normativity, based on diverse sanitary and moral concerns, into an international policy and its enactment in the Middle East. Who were the activists and lobbyists favouring drug prohibition ? What kind of normative discourses did they produce to justify that policy ? Whom were they connected around and with within the League ? What were the effects of the internationalization of drug policies within the individual mandates ? What kind of expertise does it produce, on a local level and in Geneva ? While the focus of drug control was on the main producer countries, its concern with the Middle Eastern mandates is of interest for a range of reasons. First, these mandates were under scrutiny as producers of hemp, and as for Iraq, as a possible way for opium from Persia, an important producer, to Europe. Second, the charter of the different mandates included special attention, on the part of the mandatory powers, on the traffic of narcotics. Hence, the Permanent Mandate Commission, where the mandatory reports on that and other issues were discussed on a yearly basis, became a site for the discussion on procedures of control and expertise on prohibition. Lastly, the mandates were a matter of special interests for all kinds of social, colonial and moral reformers in the aftermath of World War I, who lobbied the League on the issue of narcotics. Thus, the prohibition of narcotics offers enlightening insights into the setting up of international governance, that is at work in the Middle East to this day.