Gulf States and Iran: The Implications of Hosting Military Bases Under Jus ad Bellum and Jus in Bello (Part II)

[Chiara Redaelli is research fellow at the University of Geneva, Faculty of Law, and IHL/ICL expert for IDLO, Kyiv office. She is also co-editor in chief of the Journal on the Use of Force in International Law and co-chair of the IHL Progressive Development Platform of Ukraine. 

Antonio Bultrini is Associate Professor of International Law at the University of Florence, Visiting Professor at the Sant’Anna School of Advanced Studies (Pisa) and teaches the law of armed conflict for the Italian Air Force and Navy. He is a member of the International Law Association’s Committee on the Use of Force, part of the Multidisciplinary Network on Sanctions (MINOS) and a former official of the Council of Europe.]

This is part II of a two part series. Part I available here.

Scenario Three: Use of the Bases to Launch Attacks 

In the first part of this post, we addressed situations in which bases are used to support the war effort – such as for the transit of military personnel, weapons, and fuel – without serving as launch points for attacks. We now turn to cases in which bases are used as direct platforms for launching attacks.

Jus ad Bellum: Aggression and Iran’s Right to Self-defence

The Gulf states’ conduct could fall within the scope of Article 3(f) of General Assembly Resolution 3314, which defines as an act of aggression “the action of a State in allowing its territory, which it has placed at the disposal of another State, to be used by that other State for perpetrating an act of aggression against a third State.” The text requires actual use of the territory to launch attacks: the mere existence of a base or a bilateral defense agreement does not, as such, engage Article 3(f). 

Publicly available information does not always identify the precise launch base for each strike in the current campaign, but it indicates that Gulf host states function as forward operating hubs rather than merely passive hosts. The United States has conducted its air campaign against Iran using assets based both in its own territory and at forward installations in the Gulf. In particular, Al Udeid Air Base in Qatar, the largest U.S. installation in the region, has hosted U.S. missile systems deployed in anticipation of strikes on Iran, and was itself hit by Iranian missiles in what Tehran and multiple observers described as retaliation for U.S. attacks on Iranian nuclear facilities. Al Dhafra Air Base in the United Arab Emirates, a key U.S. Air Force hub south of Abu Dhabi that hosts the 380th Air Expeditionary Wing and advanced U.S. aircraft, has likewise been struck by Iranian drone and missile attacks.

If the United States launches attacks from those bases, Iran would have a strong argument that it may, in exercising its right of self-defence against the United States, direct force against the bases from which the armed attack is being conducted. The precedent from the June 2025 “Twelve-Day War” is instructive. When the United States struck three Iranian nuclear facilities, Iran responded by launching a volley of ballistic missiles at Al Udeid Air Base in Qatar, explicitly presenting the attack as retaliation for U.S. airstrikes on its nuclear programme. Qatar did not dispute that Al Udeid is a major U.S. installation on their soil; their statements instead condemned the Iranian missile attack as an unacceptable violation of Qatar’s sovereignty and stressed the risk to civilian areas and critical infrastructure.

Under jus ad bellum, Iran can use force in self-defence only when it is the victim of an armed attack. Therefore, the question is whether letting the United States use their territory to launch armed attacks constitutes, in itself, an armed attack within the meaning of Article 51 of the Charter. 

As it is well known, the ICJ in the Nicaragua case (§191) distinguished between the ‘most grave’ forms of force that qualify as an armed attack and lesser forms of use of force or assistance, which do not in themselves generate a right of self-defence vis-à-vis the assisting State. On a strict reading, the mere fact that a State allows its territory to be used for another State’s operations does not automatically transform its conduct into participation in an armed attack. It depends on the use of such territory. When foreign bases on its territory provide indispensable launch, command, and support functions for an ongoing armed attack, in the sense that disabling them would materially impede the continuation of the strikes, the facilities concerned become part of the territorial infrastructure of that attack. In such circumstances, defensive force may lawfully be directed at those bases as part of self-defence against the primary attacker (see here). This characterization may change further if Gulf decision-making and operational structures are directly integrated into the planning and execution of the strikes, an issue addressed in Scenario Four.

In all events, Iran’s right of self-defence is constrained by the requirements of necessity and proportionality, as well as by international humanitarian law. Any defensive force directed at US bases on Gulf territory must be limited to what is required to neutralize their specific territorial contribution to the armed attack and calibrated in scale and scope to that contribution rather than to the overall gravity of the aggression. Carefully targeted strikes against the military installations actually used to launch or support attacks are therefore easier to justify than attacks against other infrastructure located in Gulf state territory, which would require a separate and much more demanding assessment under the necessity and proportionality criteria.

Jus in Bello: Aggression without Armed Conflict?

From a jus ad bellum perspective, if the United States launches attacks against Iran from bases located in the Gulf states, the latter commit an act of aggression under Article 3(f) of the Definition of Aggression. This raises a crucial jus in bello question: does that act of aggression make the Gulf states parties to an international armed conflict with Iran? The answer is not settled in positive law. However, even if territorial authorization engages jus ad bellum responsibility, the absence of Gulf state force directed against Iran means that, on the orthodox view, the IAC threshold for party status is not yet met. This asymmetry reflects the strict separation and relative independence of the jus ad bellum and jus in bello. 

A more expansive account proposes that a state becomes a co-party to an existing international armed conflict once it knowingly makes an operational contribution that is directly connected to harm to the adversary and is sufficiently integrated into the joint decision-making processes for coordinated military operations (here). On that view, intensive operational cooperation and shared targeting or planning could, in principle, suffice for party status even in the absence of the supporting state’s own kinetic force.

A structurally analogous question arose in connection with Belarus and Ukraine. In February 2022, Russia launched its full-scale invasion of Ukraine in significant part from Belarusian territory: Russian forces had massed on Belarusian soil in the preceding weeks, crossed the Ukrainian border from Belarus in a thrust toward Kyiv, and made sustained use of Belarusian airspace and infrastructure for missile strikes. The question is whether this conduct, which clearly engaged Article 3(f) responsibility under the jus ad bellum, also rendered Belarus a party to the international armed conflict for IHL purposes.

The OSCE Moscow Mechanism Expert Mission report (2022) concluded that Belarus’s role as a staging ground for Russian forces did not, without more, render it a party to the international armed conflict for IHL purposes. On the facts assumed here, the Gulf states in Scenario Three occupy an analytically similar position: they may bear responsibility under the jus ad bellum for the use of their territory, but, absent their own use of force or evidence that their armed forces and command structures are integrated into US targeting and strike-planning, they have not crossed the threshold that would make them co-parties to the conflict under IHL.

Scenario Four: Gulf States Directly Contribute to the US Operations

Scenario Four posits the most legally consequential configuration in which the Gulf states do not merely permit US forces to operate from their territory under pre-existing treaty arrangements, but actively contribute to those operations. This encompasses a range of potential conduct, from the integration of Gulf state military personnel into base command structures and intelligence-sharing arrangements, to the direct provision of targeting data, the participation of Gulf armed forces in support missions, and the opening of national airspace for coordinated strike operations. 

Jus ad Bellum: Aggression

The first consequence of active Gulf state participation concerns the characterization of that participation under the jus ad bellum. Where a Gulf state’s own military personnel and infrastructure become operationally integrated into attack planning or execution, the conduct falls within Article 3(a) of General Assembly Resolution 3314 (Definition of Aggression), which addresses the direct use of a state’s armed forces against another state. 

The implications for state responsibility are correspondingly significant. Whereas Scenario Two primarily engaged ARSIWA Article 16, which governs responsibility for aid or assistance, Scenario Four additionally brings into play Article 17, on direction and control. A Gulf state that exerts operative influence over specific strike packages – by approving target sets, directing or vetting mission profiles, or integrating its command-and-control systems with those of U.S. forces – moves beyond mere facilitation into a position of shared direction and control over the commission of the wrongful act. 

The armed-attack question that remained contested in Scenario Three is consequently resolved more clearly in Scenario Four. In the Nicaragua case, the International Court of Justice drew a sharp distinction between the “provision of weapons or logistical or other support” to armed groups, which may amount to an unlawful use of force or intervention, and an “armed attack” in the sense of Article 51. Where Gulf state armed forces, or other persons whose conduct is attributable to those states, themselves participate in attacks on Iranian territory or forces, the conduct no longer falls within the category of assistance to a principal wrongdoer but constitutes the principal wrongful act (see also the Court’s reasoning in the Congo case).

Jus in Bello: Belligerency

The transition from passive facilitation to active participation has equally decisive consequences under the jus in bello. The ICRC’s 2016 Commentary on the First Geneva Convention restated that a state party to an international armed conflict is a state whose armed forces are engaged in the armed conflict, whether directly or as part of a broader force structure. 

The ICRC’s “support-based approach” has addressed this threshold with increasing precision. The relevant inquiry is whether a State’s contribution to another belligerent’s operations remains at the level of “mere” support – such as the provision of training or equipment – or whether it amounts to actions related to the conduct of hostilities that have a direct impact on the enemy’s ability to carry out military operations and are integrated into the collective conduct of hostilities. Support that is operationally integrated into the campaign – such as the forward transport of troops, the provision of intelligence used immediately in attacks, or the involvement of State-attributed personnel in planning and coordinating military operations – will be treated as part of the collective conduct of hostilities and may render the supporting State a party. The decisive factor is thus the degree of operational and decision-making involvement of the supporting State’s authorities in the conduct of hostilities, including how far their use of bases and infrastructure is woven into the targeting, planning and execution of strikes (here).

The legal consequences of belligerent status are substantial. Gulf state territory and military assets become lawful targets under international humanitarian law for the duration of active hostilities, as long as they qualify as military objectives; Gulf state military personnel captured by Iranian forces acquire prisoner-of-war status under the Third Geneva Convention; and the Gulf states bear direct IHL obligations, including the duty to investigate violations attributed to their forces and to ensure compliance with the law of armed conflict by those operating under their command. Once the threshold of direct participation in hostilities is crossed, the full architecture of the jus in bello applies.

Conclusions

The four scenarios traced in this article show that the legal position of the Gulf host states vis-à-vis the US–Israeli campaign against Iran cannot be captured by a single label such as “neutrality”, “non-belligerency”, or “co-belligerency”. Instead, different layers of jus ad bellum and jus in bello responsibility are activated as one moves from passive basing arrangements to operational integration in the conduct of hostilities. Once Gulf state forces or other attributable personnel are operationally integrated into the strike architecture – through shared targeting, combined planning, or participation in offensive missions – the applicable framework shifts from complicity to co-authorship of aggression in the sense of General Assembly Resolution 3314 and Articles 3(a) and 3(f), and from Article 16 to Article 17 ARSIWA on direction and control. Under IHL, the same operational integration would, on the ICRC’s support-based approach, mark the transition from non-belligerent support to full party status in the armed conflict.

The legal consequences extend in both directions. For Iran, properly characterizing the Gulf states’ conduct matters for calibrating its responses: derivative complicity in aggression may justify robust non-forcible countermeasures and claims for reparation, but not force; use of bases as a launch point for attacks would authorize self-defence action directed at the bases; direct participation in attacks can, in principle, ground full self-defence action. For the Gulf states, the central message is cautionary. Hosting foreign bases in itself does not make them belligerents, but allowing those installations and national command structures to become embedded in unlawful strike operations risks transforming them from passive facilitators into co-aggressors and possibly even co-parties to the conflict.