The number of participants in an online dispute resolution(ODR) system is crucial to its survival. Securing participation is nonetheless difficult. Clearly, it is important to offer a system that is fair, transparent and offers an efficient service at low cost. These factors are fundamental to ensure trust and to build a returning customer base to the system, but are not what attracts a party to submit a dispute for settlement. This paper describes and discusses four main categories of legal measures found in the online dispute resolution services offered by SquareTrade and WIPO. In spite of shortcomings in the offered, the legal measures have contributed to attract large numbers of participants. Large participation secures the long-term economic viability of an online dispute resolution system. The four categories of legal measures described and discussed in this paper need to be part of the specifications and the design and development of future ODR system.