The underpin of political thought plays a critical role in buttressing the principle of legality—a foundational precept in criminal law. In the modern era, this principle has primarily emerged from key political ideas, such as the rule of law, the separation of powers, social contract theory, constitutionalism, democratic governance, and good governance. This article aims to revisit the relationship between the rule of law and the principle of legality in criminal law through the lens of political philosophy. By engaging with the views of political thinkers, it offers a more precise understanding of the origins, requirements, and implications of the legality principle.
Over the past two centuries, one of the most pressing societal concerns has been the establishment of the rule of law and the consistent application of the legality principle in criminal law. This framework is essential to balancing freedom and security—ensuring that civil liberties are not sacrificed for the sake of public order, nor is public order undermined by unchecked freedom. However, the absence of robust theoretical analysis has hindered progress toward this goal, resulting in a criminal justice system that is often imbalanced and ineffective. The rule of law requires that the relationship between the state and its citizens be regulated entirely by law. Within this framework, criminal law—as the most sensitive and consequential branch of public law in governing state-individual relations—must be developed and applied strictly in accordance with legal principles. As such, the rule of law finds its most significant and practical expression in criminal law, compelling governments to employ penal measures only as necessary and to the minimal extent required to maintain public order and security. In doing so, criminal law can achieve its intended efficiency and effectiveness.