This paper studies the lessons of principled anti-corruption experts who dared to fulfill their duty of justice in highly corrupt societies, through the true story of Ngozi Okonjo-Iweala, the former Finance Minister of Nigeria. My thesis is that when principled anti-corruption experts are epistemic trespassers, they show moral incompetence. Okonjo-Iweala shows moral incompetence in two ways: she misread the opposition to her strategies and misled other honest reformers. Both actions bungled her efforts to eradicate corruption inasmuch as they hindered the (...) possibility of finding successful anti-corruption policies. Okonjo-Iweala’s moral incompetence is, I argue, the result of her epistemic trespassing that led her to act like an expert in an environment where she was not. I conclude that, in highly corrupt societies, principled anti-corruption experts should embrace moral humility, stop thinking that they are experts, and act more like students, asking questions and not rushing to think that they understand the answers. (shrink)