A critical analysis of the applicability of customary international law in Uganda: the case of Uganda Vs Thomas Kwoyelo

Abstract

This research critically analysed the legal implications surrounding the applicability of Customary International Law (CIL) in Uganda, a state rooted in the dualist tradition. The research investigates the domestic legal regime governing the reception of CIL, focusing on the inherent tension between the state's international obligation to prosecute grave crimes and its constitutional commitment to the principle of legality (nullum crimen sine lege). The legal crucible examined is the landmark case of Uganda v. Thomas Kwoyelo, where the International Crimes Division of the High Court relied on uncodified CIL to charge the accused with war crimes. Using a doctrinal and analytical research approach, supported by qualitative data, the research assesses whether the direct judicial application of CIL in the criminal case of Uganda v. Thomas Kwoyelo compromises the constitutional safeguard of legality. The findings revealed that the judicial decision to directly apply uncodified CIL, while crucial for advancing accountability during a legal lacuna, created significant legal uncertainty. This approach challenged a strict, formalist interpretation of the principle of legality under the 1995 Constitution. This outcome highlights a systemic weakness in Uganda's domestication framework for International Criminal Law (ICL), particularly regarding the mandatory requirement for certainty and clarity in criminal statutes. The research concludes by recommending the urgent codification and domestication of core aspects of customary international criminal law to enhance legal clarity, certainty, and consistency. This action would successfully safeguard fundamental constitutional rights while simultaneously ensuring the effective and legitimate prosecution of mass atrocities in the future. The originality of this research lies in its critical synthesis of strict adherence to legality and TWAIL to resolve the dualist dilemma. By applying a TWAIL lens, the study critically deconstructs the dualist dilemma, examining how post-colonial domestic courts can balance universal human rights accountability with localized constitutional integrity without yielding to arbitrary judicial legislation. Ultimately, the research concludes by recommending urgent legislative reform centered on the prospective codification and complete domestication of remaining core customary international crimes. By enacting comprehensive domestic statutes that clearly define customary international offenses and their corresponding penalties, Uganda can bridge the structural gap between municipal law and international accountability norms. Implementing these statutory reforms will eliminate future legal ambiguities, safeguard fundamental rights to a fair trial, and ensure that the domestic prosecution of mass atrocities remains both constitutionally legitimate and internationally compliant.