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.[4][5] 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: