The League of Nations adopted several drug control treaties prior to World War II, such as the International Opium Convention, and "International Convention relating to Dangerous Drugs (1925)" specifying uniform controls on addictive drugs such as cocaine and opium, and its derivatives. However, the lists of substances to be controlled were fixed in the treaties' text; consequently, it is necessary to periodically amend or supersede the conventions through the introduction of new treaties to keep up with advances in chemistry. In a 1954 interview with Harry J. Anslinger, who was the United States Commissioner of Narcotics at the time, the cumbersome process of conference and state-by-state ratification could last for a period of numerous decades.