This investigation examines a teachers’ local (local 22 of the National Union of Education Workers of Mexico (SNTE)) in the Mexican state of Oaxaca and the effects of repression on the oligarchization of local 22. Using sociologist Robert Michels’ theory of oligarchization known as the “iron law of oligarchy”—which claims that any democratic organization that becomes large enough to bureaucratize will inevitably become an oligarchy—as a framework, this investigation makes the argument that external influences, specifically government repression, can force an organization to become oligarchic, thus occupying an important, yet unexplored space within the “iron law” theory. Michels’ theory focuses on an organizations’ internal issues such as bureaucratization, centralization of power, and technical specialization of job positions as the factors that push an organization to become oligarchic without accounting for external issues faced by organizations that can also influence a shift to oligarchy. Through historical research, interviews of local 22 members, and observations carried out in Oaxaca City this investigation argues that intense government repression and violence against local 22 beginning in 2006 and continuing for the next ten years significantly affected local 22’s shift toward oligarchy, more so than the bureaucratization and centralization that took place within the local.