The Application of Customary Criminal Law from Perspective of The Legality Principle and Legal Certainty

Customary criminal law is part of the living law within society and reflects the values, customs, and sense of justice of customary communities. The recognition of living law has a normative basis in Law Number 1 of 2023 concerning the Criminal Code (KUHP), particularly Article 2. However, this recognition raises issues regarding the relationship between legal pluralism and the principle of legality, which requires a clear legal basis for criminal punishment. This article aims to analyze the application of customary criminal law from the perspectives of the principle of legality and legal certainty. This study employs a normative juridical method using statutory and conceptual approaches through an examination of primary legal materials and scholarly literature. The findings indicate that customary criminal law may be accommodated provided that it complies with constitutional limitations, does not conflict with Pancasila, the 1945 Constitution of the Republic of Indonesia, human rights, and general legal principles recognized by the community of nations, and is applied through transparent and reviewable procedures. Legal certainty must be maintained by carefully identifying customary communities and their customary norms, establishing that such norms genuinely remain in force within the community, and ensuring that the sanctions imposed are proportionate and respect the rights of all parties involved.