In the years after independence, former British colonies in eastern and southern Africa struggled to fill the ranks of their judiciaries with African judges. Beginning in the mid-1960s, states including Uganda, Tanzania, and Botswana solved this problem by retaining judges from the Caribbean and West Africa, especially Nigeria. In this same period, a wave of coups brought many independent states under the rule of their militaries (or authoritarian civilian regimes). Foreign judges who had been appointed in the name of pan-African cooperation were tasked with interpreting the laws that soldiers imposed, and assessing the legitimacy of regimes born of coups. The decisions they rendered usually accommodated authoritarianism, but they could also be turned against it. To understand how colonial law and postcolonial solidarities shaped Africa's military dictatorships, this article focuses on one judge, Sir Egbert Udo Udoma of Nigeria, who served as Uganda's first African chief justice and was an influential member of the Nigerian Supreme Court. Udoma and other judges like him traversed the continent in the name of African cooperation, making a new body of jurisprudence as they did so. Their rulings were portable, and they came to underpin military rule in many states, both in Africa and in the wider Commonwealth.