‌Context & Objective: The concept of public interest constitutes a fundamental paradigm within public law, serving as the ultimate objective of the state and the guiding principle for the legislative, executive, and judicial branches. Historically, the European legal tradition navigated diverse interpretations, encompassing the Platonic aristocratic model, the republican social contract, state expediency, and the liberal pursuit of maximum utility. Concurrently, within Islamic political thought, public welfare is pursued through foundational mechanisms such as expediency, justice, the rule of no-harm [La-Zarar], and public administration. Following the establishment of the Islamic Republic of Iran, the national legislative architecture integrated religious tenets with modern governance institutions, explicitly rejecting secularism's strict separation of religion and politics. This dual legal and religious order requires all legal norms to comply with Islamic criteria, yet applying traditional jurisprudence (Fiqh, the profound understanding of Islamic rulings) to complex contemporary realities presents unprecedented administrative challenges. While the system initially relied on secondary titles and situational governmental decrees, a fundamental legal question persists regarding how to ensure dynamic societal administration without deviating from eternal religious principles. Accordingly, the primary objective of this research is to analytically elucidate the tripartite functions of the Maqāṣid al-Šarīʿa (the higher objectives and purposes of Islamic law) within the Iranian legal system, demonstrating that the macro-goals of this government align seamlessly with jurisprudential objectives to effectively secure the public interest.
 ‌Method & Approach: The methodological framework of this research relies on doctrinal legal analysis, adopting a descriptive-analytical approach. Data acquisition is systematically conducted through library research and the documentary review of classical jurisprudential treatises, formal statutory laws, and the Constitution. The data analysis applies rational argumentation and jurisprudential-legal deduction to extract the functional capacities of the overarching legal objectives. Philosophically, this analysis is predicated on four essential presuppositions: religious law possesses definitive goals, legal rulings are contingent upon inherent benefits and harms, the human intellect possesses the capacity to discover these legislative intents, and the scope of legal deduction encompasses the entirety of the public sphere. Acknowledging varied historical methodologies—ranging from strict textualism that ignores overarching objectives to extreme purposivism that incorrectly prioritizes overarching goals over explicit statutory texts—this study adopts a progressive, moderate, and text-based interpretative paradigm.
 ‌Findings: The constitutional mandate regarding "Islamic rules" provides the structural pathway for integrating Maqāṣid al-Šarīʿa into the Iranian legal architecture through three distinct mechanisms. First, the independent function serves as an autonomous source for deriving original legal norms concerning emerging public issues. It justifies the establishment of the state itself and guides macro-system design in novel areas such as economic smuggling regulations and artificial intelligence governance. Second, the instrumental function establishes the overarching objectives as the supreme interpretative criterion for maintaining normative consistency across the constitutional and statutory hierarchy. Through this purposive lens, restrictive interpretations are broadened; for example, the constitutional requirement for presidential candidates to be political and religious figures can be interpreted through the objective of meritocracy to encompass female candidates. Third, the complementary function operates as the ultimate adjudicative standard for resolving normative conflicts by prioritizing the most vital public interest. This priority mechanism legally justifies overriding secondary principles, such as permitting the medical dissection of cadavers for scientific advancement, restricting private property rights for essential public infrastructure, and recalibrating penal responses based on societal necessity.
 ‌Conclusion: The systematic integration of Maqāṣid al-Šarīʿa into the Iranian legal framework represents the establishment of an indigenous, religion-based discourse for modern state administration, rather than a theoretical concession to Western modernity. By deploying a moderate and rational jurisprudential approach, this purposive theory significantly elevates the legal system's structural capacity to resolve the intricate complexities of contemporary governance. The overarching objectives function as the paramount regulatory mechanism guaranteeing normative coherence and procedural justice across all echelons of public law. Crucially, the implementation of the independent, instrumental, and complementary functions facilitates substantial systemic flexibility. It permits the prioritization of human dignity (Karāmat-e Insāni, the inherent nobility of humanity) and the preservation of societal faith, which rationalizes the suspension of severe corporal punishments and the expansion of rehabilitative legal mechanisms like repentance.