Personal security, as a fundamental right and a criterion for assessing the legitimacy of public power, despite legal recognition in Iran’s legal system, faces serious shortcomings at the implementation stage. Normative recognition has not necessarily resulted in effective guarantees in legislation and adjudication, leaving individual freedoms exposed to extensive and sometimes unnecessary interventions. From this perspective, this study adopts a critical–analytical approach to explain the persistence of the gap between normative commitments to personal security and its practical realization, a gap reproduced in the absence of clear standards for assessing the legitimacy of intervention and binding institutional safeguards. Analysis of the shared foundations of constitutional and criminal law shows that this condition is not incidental, but the combined outcome of conceptual ambiguity in criminalization, the dominance of security-oriented interpretations of public interest, and weaknesses in institutional enforcement structures. Based on a comparative study of international human rights instruments, judicial practices, and selected legal systems, a three-level framework is proposed to reconstruct and guarantee the legal protection of personal security, centered on the four-part test of legitimacy of intervention. This test operates as a limiting standard in legislation, an analytical obligation in adjudication, and a mechanism of accountability and enforcement in oversight. The findings indicate that transforming fundamental principles of public law from abstract commitments into enforceable and reviewable obligations is essential for making personal security a real measure of the legitimacy and effectiveness of public power.