Mexico is at a crossroads in terms of drug policy. The judicial route has recently positioned itself as a possible tool to dismantle a century of prohibitionism that, in its historical development, has resulted in significant grievances for the country. The purpose of this article is to understand the ruling that declared the absolute prohibition of cannabis unconstitutional in 2018. The main premises and argumentation techniques were identified through an argumentative analysis. The results reveal a display of hierarchies, facts, values, presumptions and commonplaces that lead to the liberal premise of allowing that which does not harm third parties. Despite ruling in favor of individual liberty, the judgement represents a reform of prohibitionism.