During the seven-year Syrian civil war, a driver of instability in the Middle East, Iran has been one of the key regional powers that has intervened to support President Bashar Al-Assad’s regime, based on its geopolitical interests in the Middle East.

This analysis addresses the events leading up to the conflict in Syria, with a focus on the legality and impact of the Iranian military intervention in the Syrian civil war.

Military intervention in armed conflicts must have a legal basis to justify the taking of action, otherwise it violates the principle of the prohibition of the use of force, under Article 2(4) of the United Nations (UN) Charter. Article 2(4) prohibits the threat of, or use of, force against the territorial integrity or political independence of any State. In this regard, invitation or consent by the host State involved in a civil war is one of the three justifications which constitute a legal basis for military intervention by the third States, in order to assist the host State to defend itself. These three justifications being: use of force authorised by the UN Security Council, use of force for humanitrainal objectives, and self-defence. Certainly, military intervention by invitation or consent of the host State, is also an exception to the principle of sovereign equality of States. This provides that the territorial integrity and political independence of States are inviolable. In a sense, sovereign equality is based on the States’ committment to respect the personality of other States. This means that they should refrain from any intervention in the other States’ territory which may threaten the personality of the State, or its political, economic and cultural elements, thus contravening international law.

Military intervention by invitation is, in fact, the consent of a legitimate government of a victim-State (which is confronted with an armed conflict) given to another State to use armed force against its enemies. The victim State may invite allies to assist it in using armed force in self-defence. The legality of military intervention by invitation has been confirmed by UN General Assembly Resolution 3314, in which the General Assembly recognises, indirectly, the validity of military intervention by invitation. According to Article 3(e) of the Resolution “the use of armed forces of one State which are within the territory of another State with the agreement of the receiving State [is an act of aggression where it is] in contravention of the conditions provided for in the agreement or any extension of their presence in such territory beyond the termination of the agreement”. However, the permissibility of intervention by invitation in civil wars is a controversial topic in international legal practice. Legal support for unlawful intervention in civil wars is also found in the 1975 Resolution of the Institute of International Law on ‘The Principle of Non-Intervention in Civil Wars’, in which civil wars are defined as non-international armed conflicts between the government of a State and insurgent movements, whose aim is to overthrow the government or the political, economic or social order of the State, or to achieve secession or self-government for any part of the State; or non-international armed conflict between two or more groups contending for control of the State in the absence of an established government. Nevertheless, there is evidence of State practice (including the US and Coalition States, who find host State consent as a justification of intervention in a civil war) which is mostly based on the permissibility of intervention by invitation in civil wars.

Based upon State practice, therefore, it seems that there is no question of violation of the obligation to refrain from the use of force in Syria, due to the consent and invitation of Bashar Al-Assad’s regime, as the internationally-recognised legitimate government of Syria, which has effective control over its territory and has not been replaced by another political entity. In other words, the consent of Bashar Al-Asad as an official of the Syrian government, who was elected in accordance with the Syrian Constitution, constitutes a justification for third-State intervention in Syria. As A. Cassese pointed out, “by explicit consent, a State may authorize the use of force on its territory whenever, being the object of an “armed attack”, it resorts to individual self-defence, and in addition authorizes the third State to assist in collective self-defence” (A. Cassese, International Law, Oxford: 2001, p. 101).

In this respect, the jurisprudence of the International Court of Justice (ICJ) is more illustrative. In the Nicaragua Case (para. 246) it states that, contrary to the incompatibility of military intervention by a mere request for assistance made by an opposition group in another State with the principle of non-intervention (as a customary international law), military intervention is already allowable at the request of the government of a State. In terms of the ICJ’s confirmation in the Nicaragua Case (para. 199), and the case concerning Armed Activities on the Territory of the Congo (paras. 43, 50), there is no rule permitting the use of force in collective self-defence in the absence of a request by the State [or where the host State consents to another State’s use of force in its territory] which regards itself as the victim of an armed attack. This is exactly why Iran’s Minister of Defense stated that Iran is in Syria as a result of a Syrian government request to support the country’s legal government, and that if the Syrian government says that there is no need for the presence of Iranian advisors, there will be no reason to continue being in the country. In other words, all actions to support the Syrian regime, the key element of which is to safeguard the survival of Syria’s embattled President Bashar Al-Assad, have been taken in response to an invitation from the legitimate Syrian government, in compliance with UN Charter Article 2(4).

Nevertheless, the widely-accepted view is that military intervention in a civil war, in particular when its objective is to support an established government against its own population, is unlawful, even if by invitation of the host State. In the case of the Syrian civil war, therefore, it seems that military intervention ─directly or indirectly─ on behalf of the Syrian government, which has committed war crimes by targeting civilians on many occasions, is a violation of the obligation of third States to refrain from giving assistance in violation of international law, through participation in war crimes and actions rising to the level of crimes against humanity. At this point, Iran, as a third party intervening in the Syrian civil war by invitation of the Syrian government, is obligated to ensure respect for the rules of humanitarian law.

To summarise, continuing to assist the Syrian regime, whilst there is much evidence that Syria is committing war crimes inside its borders, entails the envolved States’ international responsibility for supporting, and closing its eyes to, the violation of humanitarian law and war crimes committed against civilians in Syria. In such a case, the war crimes of the host State, supported by its allies, constitute a legitimate basis for military intervention by third parties for humanitarian objectives and with a view to end serious human rights violations.