What role did law play in articulating sovereignty and citizenship in postcolonial Africa? Using legal records from the secessionist Republic of Biafra, this article analyzes the relationship between law and national identity in an extreme context—that of the Nigerian Civil War (1967–1970). Ideas about order, discipline, and legal process were at the heart of Biafra's sense of itself as a nation, and they served as the rhetorical justification for its secession from Nigeria. But they were not only rhetoric. In the turmoil of the ensuing civil war, Biafra's courts became the center of its national culture, and law became its most important administrative implement. In court, Biafrans argued over what behaviors were permissible in wartime, and judges used law to draw the boundaries of the new country's national identity. That law played this role in Biafra shows something broader about African politics: law, bureaucracy, and paperwork meant more to state-making than declensionist views of postcolonial Africa usually allow. Biafra failed as a political project, but it has important implications for the study of law in postcolonial Africa, and for the nation-state form in general.