Niklas Luhmann's sociology proposes that law is an autonomous social system, which cannot be determined from the outside. In this theoretical framework, law's relations with its environment are mainly grasped with the concepts of autopoiesis and deparadoxification, and through the corresponding paradox of openness through closure. It provides a framework to explore intersystemic relations which refuses a vertical, linear domination of law by other discursive formations. This paper takes (some dimensions of) the 2003 re-validation of the constitutionality of the prohibition of cannabis by the Supreme Court of Canada as a pretext to theoretically clarify and empirically explore this framework. In the case presented here, law notably gives precedence to some biomedical objects over the liberal doctrine. It may well do the exact opposite in future operations. Sociology is condemned to be surprised by the creativity that law displays in autonomously maintaining and transforming itself.