The global anti-doping effort in sport is based upon perceptions of the system as desirable, proper and appropriate and thus considered legitimate. The legitimacy of the anti-doping system has earlier been studied bottom-up, based on the views of athletes. In order to gain greater understanding of legitimation processes, it is also important to study legitimation strategies top-down, used by decision-making and governing bodies. The aim of this study was to use Fairclough's critical discourse analytical approach to analyse the social construction of legitimacy in the World Anti-Doping Agency's three editions of a guide to anti-doping rules aimed at athletes. The analysis was performed based on van Leeuwen's four specific legitimation strategies: authorization, rationalization, moral evaluation and mythopoesis. Our analysis shows that the legitimation of the anti-doping discourse as constructed in the athlete guides that has accompanied anti-doping regulations for more than a decade is characterized by continuity as regards an authoritarian attitude, but also by change towards a more rational and athlete-centred stance. A shift can be seen in the construction of legitimacy in the anti-doping discourse from “fighting the bad” to “protecting the good”. We discuss the moral evaluation strategy as a way to construct legitimacy for anti-doping efforts and sport in general towards a wider public. In the light of the results of this study, we conclude that policymaking in relation to doping issues should take into account the dimension of the discursive top-down legitimation, which could affect how the policy is received at the level of the athletes and provide conditions for a sustainable anti-doping system.