This is an old piece that is nonetheless fascinating:
Large-scale Nigerian migration to China began in the aftermath of the 1980s Deng Xiaoping reforms, which opened China to the international community. The first wave of Nigerian migrants to China arrived in the late 1990s.
…. The Nigerian community in China has elected officials who preside over matters affecting their members. The post of ‘President General’ is an elected position, in line with a Constitution that gives anyone holding office term limits of two tenures. As of March 2016, the President General had completed the tenure of his predecessor who stepped down and another election was planned towards the end of the year. The President General organizes the community, ensuring that safety, representation and support are accessible. The Nigerian migrant community is also made up of sub-communities between which the President General solves power imbalances.
….. There is an informal justice system within the Nigerian community in China that facilitates dispute resolution at a micro level—which, practically, the Chinese government cannot enforce due to the clandestine existence of many individuals. In my interview with Mr. T (not real name), he stated that the Nigerian community has a task force that handles policing on behalf of the community.
The justice system is presided over by executives (judges) who settle cases brought before them. According to a member of the community, the judges are elected and not appointed. They are often people well respected within and outside the community; as a result, people obey their directives.