In this article, Mark James and Guy Osborn discuss how the relationships between the various members of the Olympic Movement are governed by the Olympic Charter and the legal framework within which an edition of the Olympic Games is organised. The legal status of the Charter and its interpretation by the Court of Arbitration for Sport are examined to identify who is subject to its terms and how challenges to its requirements can be made. Finally, by using the UK legislation that has been enacted to regulate advertising and trading at London 2012, the far-reaching and sometimes unexpected reach of Olympic Law is explored.