This chapter reflects on the diversity of usages of the notion of transnational law in legal scholarship. To do so, it focuses on the lex sportiva as a fruitful empirical field to study in concreto the use of the concept. Indeed, the regulation of international sports is nowadays often referred to as lex sportiva and deemed an example of transnational law. The first part of this chapter retraces how lex sportiva has been used as empirical evidence for a ‘pure’ theory of transnational law, a conception of transnational law as denationalized legal order of a transnational community. The second part will aim to show how lex sportiva can also be used to support an ‘impure’ theory of transnational law, which might better capture the messy process of transnational interactions between multiple levels, norms and institutions that characterizes much of contemporary legal practice.