This chapter looks at the use of martial law to detain and try British subjects in the Cape and Natal in the Anglo-Boer War, and the legal questions raised. Since the legal nature of martial law was still contested, its ambit was a matter of negotiation between various parties, military and civilian, imperial and colonial. This is shown through the debates over the creation and role of a special court to deal with rebels, and over the introduction of a limited form of martial law in the Cape ports. The right of the military to detain under martial law was repeatedly challenged in litigation which revealed that the attitude of the judges in the Cape courts was often much more liberal than that of those in the Privy Council. The Cape legislature was also unwilling to indemnify the military for its actions unless the sentences of those held in prison as a result of martial law trials were reviewed and revised. This chapter shows that, while Cape politicians often sought to rein in martial law powers by subjecting them to common law tests, both the military authorities and judges in London were more prepared to concede the executive exceptional powers in times of perceived emergency.