The ‘lawmaking’ of arbitral institutions has been a recurring issue in international arbitration. It is widely accepted that international arbitral tribunals do not have a forum , thus are relatively autonomous from the legal orders constituted by the states. Nevertheless, their adjudicative powers are always limited by the concept of international (transnational) public policy. Due to that arbitral institutions often aim at the creation of a consistent jurisprudence based on the universally accepted general principles of law. This has also been true for sport arbitration, where the ‘supreme court’ for sport CAS developed a set of principles called lex sportiva, governing transnational sport competition. Nonetheless, in sport, also BAT—established to solve contractual disputes in basketball—has become a true ‘lawmaker’. The uniqueness of BAT arbitration creates vast opportunities to unveil the general principles of law governing contractual relations in basketball. At the heart of it lies the default decisional standard ex aequo et bono that allows arbitrators for a certain degree of flexibility in their decision-making. In addition, a simple and flexible procedure equips them with a unique power over arbitration process. Finally, the voluntary character of BAT arbitration (unparalleled in sport arbitration) and its popularity within the basketball community reinforces arbitrators’ mandate to decide what is just and fair in basketball contracts. Due to that BAT established a significant presence in the landscape of sport arbitration and contributed to the development of contractual standards that global basketball relies on.