When, how, and why—if at all—did slavery end in the Nigerien Sahel? What processes facilitated the emancipation of enslaved persons? What were the strategies of colonial administrators, slave-owners, slave-traders, slaves, and slave descendants? In the first two decades following France’s occupation of the Central Sahel, legal abolition did not lead to the suppression of slavery, because laws were not at first enforced. But in the 1920s the internationalization of abolitionism that followed the creation of the League of Nations resulted in the activation of anti-slavery laws. This article argues that emancipation was initially propelled by the establishment of international surveillance mechanisms with the power to (de-)legitimize colonial rule at a time when no one was actively seeking to end slavery in this region. The first section highlights the ambiguities of European abolitionism and reveals the web of connections between the League of Nations, the French state, and French administrators on the ground. The second section develops a microanalysis of slave resistance, showing how some enslaved and trafficked persons, especially young women, profited from global institutional transformations to incriminate their owners and traffickers. The final section considers the contemporary recollections of an elderly woman, who in her youth experienced circumstances analogous to those described earlier in the article. Her perceptions, and those of others like her, exist today in a context marked by tension between circumscribed proslavery discourses and national grassroots abolitionism.