Reconfiguring the Principle of Legality in Indonesia’s New Criminal Code: Between Legal Certainty and Living Law

The enactment of Law No. 1 of 2023 on the Indonesian Criminal Code reconfigures the principle of legality by retaining formal legality while recognizing living law as a potential basis for criminal liability. This development raises a fundamental question concerning whether the recognition of unwritten customary norms strengthens substantive justice or undermines legal certainty and protection against arbitrary punishment. This study examines the transformation of the principle of legality from Law No. 1 of 1946 to Law No. 1 of 2023 and evaluates the compatibility of living law with the requirements of lex scripta, lex praevia, lex certa, and lex stricta. The research employs a normative legal method using statutory, conceptual, historical, and internal comparative approaches. Legal materials are analyzed through grammatical, systematic, historical, teleological, and conceptual interpretation. The study finds that Article 1 of Law No. 1 of 2023 maintains the requirement of prior legal regulation and expressly prohibits the use of analogy in determining criminal offences. The non-retroactivity principle also remains applicable, subject to the lex mitior rule when subsequent legal changes are more favorable to the offender. However, Article 2 recognizes living law within society, thereby extending the sources of criminal law beyond written legislation. This construction may accommodate legal pluralism and substantive justice, but it also creates risks relating to accessibility, foreseeability, consistency, and human rights protection. The article contributes to the legality debate by arguing that living law may only be applied through strict normative safeguards, clear evidentiary standards, territorial limitations, and consistent compliance with constitutional principles, human rights, and the prohibition of analogy.