The international conference on narcotic drugs convened in Shanghai represented the first time that the actual situation related to the main producing and consuming countries was analysed in detail. In addition, the first attempts were made to reach an agreement on limiting shipments of narcotic drugs ([43], p. 283). It can thus legitimately be considered the starting point of the international drug control system. The sections that follow detail the evolution of the central concept of this system: action by individual States, within the limits of their jurisdiction, national policies, legislation and resources, in compliance with the provisions of the international drug treaties ([44], p. 63).