Thesis in criminal law, University of Parma. In my thesis I address the issue of the criminalization of cannabis: a very widespread plant in the world, which over the centuries has been the subject of an intense process of stigmatization, which has led to strictly prohibitionist laws and regulations in many countries of the world and also within of the international community, through various international treaties that have sanctioned its ban. Then, addressing the issue of drug trafficking and the illegal drug market, we intend to demonstrate, through the illustration of empirical data, the failure of the prohibitionist approach. Finally, through an examination of the most important reforms on the subject that have been adopted to date in the world (mainly in the United States).