Fauziya Kasinga left her native land of Togo for the United States in order to avoid female genital mutilation (FGM)—a traditional practice in her culture in which a woman’s clitoris is cut away in order to deaden sexual pleasure. Detained for entering the United States illegally, Kasinga spent two years in jail before being granted political asylum by the Board of Immigration Appeals in 1996.

Prior to Kasinga’s case, immigration law had granted asylum to members of any “particular social group” which was being persecuted by its government, but the law did not consider women to constitute such a group. The Kasinga ruling changed that by defining women as a “particular social group” and by including in the legal definition of “persecution” such acts against women as FGM. Few...