Legal Literacy - In the architecture of criminal law, the principle of legality (nullum delictum nulla poena sine praevia lege poenali) stands as a main pillar that guarantees legal certainty. This principle carries the logical consequence of prohibiting retroactive enforcement (non-retroaktif) of a criminal regulation. The aim is clear: to protect citizens from potential state arbitrariness that punishes actions based on rules made post-factum (after the fact).

However, law is not a static entity. It moves dynamically in response to shifts in social, political, and societal justice values. When changes occur in criminal legislation, tension arises between legal certainty and justice. This is where the principle of Lex Favor Reo is present as a vital exception to the principle of non-retroactivity, functioning as a bridge of justice in transitional law (hukum transitoir).

Basic Philosophy: Between Sword and Scales

Terminologically, Lex Favor Reo means the application of a more lenient or favorable law to the defendant. This principle affirms that if there is a change in legislation after the act is committed but before the decision has permanent legal force (inkracht), then the judge is obliged to apply the provisions that are most favorable to the defendant.

The philosophy behind this principle is humanity. If the legal awareness of society (represented by the lawmakers) has changed and views an act as no longer as evil as before—or the sanctions are considered too cruel—then it is not ethical for the state to continue to impose heavy punishments based on outdated rules that have been abandoned.