International organizations (IOs) have effectively modified the structure of international law. For more than six decades, IOs have echoed the aspirations of humankind, in pursuit of the ideal of realization of justice, and have furthermore contributed to that end. IOs are provided with privileges and immunities that are intended to ensure their independent and effective functioning. These are specified in the treaties that give rise to the organization, which are normally supplemented by further multinational agreements and national regulations under the international law. Rather than by national jurisdiction, legal accountability is intended to be ensured by legal mechanisms that are internal to the IO itself and by access to administrative tribunals. In the course of many court cases, where private parties tried to pursue claims against IOs, there has been a gradual realization that alternate means of dispute settlement are required, as states have fundamental human rights obligations to provide plaintiffs with access to court in view of their right to a fair trial. Otherwise, the organizations’ immunities may be put in question in national and international courts.