Context & Objective: The application of force within political relations remains a fundamental challenge in legal studies. In contemporary Public International Law, the principle of the non-use of force operates as a peremptory norm, with the doctrine of legitimate defense under Article 51 of the United Nations Charter serving as its primary exception. This right is conditioned upon necessity, immediacy, proportionality, and the collective security framework. Concurrently, Islamic jurisprudence (fiqh—Islamic substantive law) addresses the use of force through jihad-e difāʿī (defensive struggle), conceptualized as an inherent right and individual obligation enacted in response to aggression against the territory, life, property, or ideological foundation of the Islamic community. Consequently, the primary objective is to address the following research question: despite fundamental divergences in their underlying philosophies of legitimacy, does jihād-e difāʿī align with the doctrine of legitimate defense in contemporary international law regarding ethical constraints and structural parameters, or do intrinsic differences preclude normative convergence?
Method & Approach: The investigation employs a doctrinal methodology structured around a formal comparative approach, executed in three distinct phases. First, relevant jurisprudential sources pertaining to jihad-e difāʿī are collated, extracting the core elements governing its legal legitimacy through conceptual analysis. This involves examining foundational religious texts alongside established rational principles. Second, the procedural and substantive rules defining legitimate defense within Public International Law are delineated, relying heavily on Article 51 of the United Nations Charter, customary international law, and judicial practice. Finally, a structural comparison is conducted between the constituent elements of both legal systems. This assessment systematically evaluates the potential for normative convergence between the two frameworks across three specific levels: the basis of legitimacy, the operational conditions and constraints, and the structure of authoritative reference.
Findings: The structural comparison reveals a combination of foundational divergences and substantial practical convergences. Significant alignment exists regarding the tripartite principles of necessity, proportionality, and the protection of non-combatants. Neither system conceptualizes the use of force as an absolute right; both confine military action to a measure of last resort, strictly proportional to the actual threat. In Islamic jurisprudence, warfare regulations explicitly mandate proportionality and prohibit targeting civilians, correlating closely with international humanitarian law. However, two obstacles prevent complete alignment. First, there is a divergence in the philosophy of legitimacy. Public International Law strictly recognizes state sovereignty and territorial integrity as the sole grounds for defense against a verifiable armed attack. Conversely, Islamic jurisprudence broadens the scope to include protecting the ideological core of the Muslim community. Second, the structural authority for public mobilization differs. While the international system restricts military decision-making to state apparatuses, Islamic jurisprudence places this responsibility on the ḥākim-e šarʿ (legitimate religious ruler), stipulating that in emergencies, the obligation to defend devolves upon every capable individual without requiring formal state authorization.
Conclusion: Absolute normative convergence between the two frameworks remains impossible due to incompatible structures of authority and differing bases of legitimacy. Nevertheless, a profound capacity for mutual dialogue exists regarding operational constraints. The recent 2026 military conflict involving the United States, Israel, and Iran illustrates these complexities. From an international law perspective, preemptive strikes lacking a verifiable armed attack fail customary tests of necessity. Concurrently, from the perspective of Islamic jurisprudence, unprovoked aggression instantly activates the individual obligation of defense. This conflict highlights the failure of the United Nations Security Council to fulfill its collective mandate, underscoring the limitations of the international institutional framework. While international law provides a structured, state-centric mechanism to regulate security, institutional paralysis compromises its efficacy. Integrating the rigorous humanitarian capacities of Islamic jurisprudence with the formal structures of the international system could facilitate the development of a robust model of legitimate defense, maintaining international legal legitimacy while adhering to shared human-centric principles.