This paper adopts the approach of public authorities and legal geographies to unravel how migrant communities seek and obtain justice in the metropolis of Johannesburg while facing widespread xenophobia and marginalization. Focusing on the Somali and Ethiopian diasporas in Johannesburg, it maps the socio-legal practices through which clan elders, religious leaders, and community activists act in lieu of law-enforcement institutions such as the South African courts and police forces, to solve disputes and criminal cases involving members of their communities. It also offers insights into the state of the South African state- or its in/ability to provide justice and security for those living within its borders. The paper is based on more than one hundred interview with the Somali- and Ethiopian-migrant communities in Johannesburg and their associated ‘home’ communities in Ethiopia and Somalia. It explores how migrants select and implement justice routes among different, overlapping, and competing levels of governance and public authorities. The starting point has been to explore how the challenges migrants experience in Johannesburg - a city with a well-known reputation of high rates of crime, police corruption and xenophobia – enable the travel and diffusion of customary practices through which different public authorities perform law-enforcement beyond state jurisdiction. Bridging legal geography literature with southern urbanism scholarship and situating Johannesburg as one of the growing urban and migration hubs on the African continent, the paper introduces a debate on migrant justice in the African metropolis; explores unique and plural socio-legal dynamics that emerge with the mobilisation and urbanization of customary and socio-legal practices across African diasporas; and analyses the encounters of such practices with singular state and city-led law enforcement.