International Opium Convention

The International Opium Convention, signed at The Hague on January 23, 1912 during the First International Opium Conference, was the first international drug control treaty. The United States was unsuccessful in its attempts to have cannabis included in the 1912 Convention.It was registered in "League of Nations Treaty Series" on January 23, 1922. The United States convened a 13-nation conference of the International Opium Commission in 1909 in Shanghai, China, in response to increasing criticism of the opium trade. The treaty was signed by Germany, the United States, China, France, the United Kingdom, Italy, Japan, the Netherlands, Persia, Portugal, Russia, and Siam. The Convention provided, "The contracting Powers shall use their best endeavours to control, or to cause to be controlled, all persons manufacturing, importing, selling, distributing, and exporting morphine, cocaine, and their respective salts, as well as the buildings in which these persons carry such an industry or trade."
The Convention was implemented in 1915 by the United States, Netherlands, China, Honduras, and Norway. It went into force globally in 1919, when it was incorporated into the Treaty of Versailles.
The primary objective of the convention was to introduce restrictions on exports as opposed to imposing prohibition or criminalising the use and cultivation of opium, coca, and cannabis. That explains the withdrawal of the United States and China, which were gravitating towards prohibitionist approaches, as well as the beginning of negotiations leading to the 1925 International Opium Convention in Geneva.
A revised International Opium Convention "International Convention relating to Dangerous Drugs" was signed at Geneva on February 19, 1925, which went into effect on September 25, 1938, and was registered in "League of Nations Treaty Series" on the same day. It introduced a statistical control system to be supervised by a Permanent Central Opium Board, a body of the League of Nations. Egypt, with support from 
China and United States, recommended that a prohibition on hashish be added to the Convention, and a sub-committee proposed the following text:
The use of Indian hemp and the preparations derived therefrom may only be authorized for medical and scientific purposes. The raw resin (charas), however, which is extracted from the female tops of the cannabis sativa L, together with the various preparations (hashish, chira, esrar, diamba, etc.) of which it forms the basis, not being at present utilized for medical purposes and only being susceptible of utilisation for harmful purposes, in the same manner as other narcotics, may not be produced, sold, traded in, etc., under any circumstances whatsoever.
India and other countries objected to this language, citing social and religious customs and the prevalence of wild-growing cannabis plants that would make it difficult to enforce. Accordingly, this provision never made it into the final treaty. A compromise was made that banned exportation of "Indian hemp" to countries that have prohibited its use, and requiring importing countries to issue certificates approving the importation and stating that the shipment was required "exclusively for medical or scientific purposes." It also required Parties to "exercise an effective control of such a nature as to prevent the illicit international traffic in Indian hemp and especially in the resin." These restrictions still left considerable leeway for countries to allow production, internal trade, and use of cannabis for recreational purposes.
The Convention was superseded by the 1961 Single Convention on Narcotic Drugs.