Are Western Democracies' Airstrikes against ISIL Lawful?


A US Air Force F-15E Strike Eagle returning from strikes in Syria, 2014. Source: US Airforce


Following the 13 November Paris attack, France declared that it is “at war” with ISIL. This echoes the manner in which former US President George W Bush announced a war on terrorism as a response to the 9/11 attack and on this basis justified military intervention in Afghanistan and later Iraq.

Whereas the airstrikes carried out in Iraqi territory are lawful already because the Iraqi Government has explicitly requested the military intervention of foreign countries, Syria has never consented to military intervention by France, the U.S. and other countries in the West.

The U.N. Charter provides only two exceptions to the general prohibition of the use of force, namely when force is being used with the authorisation of the U.N. Security Council; and in situations of self-defence.

UNSC Resolution 2249 (2015)

Last month, the U.N. Security Council adopted Resolution 2249 (2015), which seems to offer some legitimacy to a military response, because it calls on Member States that have the capacity to do so to take “all necessary measures” against ISIL

But as explained by Akande and Milanovic the Resolution has “creative ambiguity”.

Firstly, the Resolution was not adopted under Chapter VII of the Charter, which would have signalled that the Security Council intends to take binding action.

Secondly, the Resolution does not “authorise” or “decide” that these measures be taken, but instead makes reference to existing international law rules.


This means that the legality of military intervention in Syria must be evaluated on the basis of a possible right to self-defence, as many government officials in Western democracies have implied exists, especially following the Paris attack.

But it is not self-evident that the Paris attack amounts to an “armed attack” within the meaning of Article 51 of the U.N. Charter, which would trigger the right to self-defence.

There is a lack of agreement concerning the term “armed attack”, but it is usually assumed that it must involve the use of military force and possibly that it must have a certain gravity or scale.

Even assuming that the Paris attack was not only a series of horrendous crimes but qualifies as an armed attack, international law is not clear on whether States can exercise their Article 51 right to self-defence against non-state actors such as ISIL.

The jurisprudence of the International Court of Justice implies the right to self-defence does not apply to non-State actors.

Recent State practice and opinion among scholars may nonetheless support the claim that a State can exercise the right to self-defence against non-state actors in situations where these actors have carried out on attack against it and operate from the territory of another State which is unwilling or unable to suppress the threat posed by the non-state actor.

Justifications for the airstrikes prior to the Paris attack

Justifying military action against ISIL under the doctrine of self-defence as a response to the Paris attack is problematic because several of the countries currently carrying out airstrikes in Syria – including the U.S. and France – were already doing this prior to that attack. Logically no right to self-defence can emerge if a State is already involved in an armed conflict.

Two arguments have been presented to justify military intervention in Syria prior to the Paris attack.

One claims legality due to the threat that ISIL poses to the intervening States; that is, a supposed right to self-defence in the form of pre-emptive strikes, since ISIL had at that point not carried out an armed attack against these States.

The second claims legality on the basis of the right to collective self-defence; that is, a supposed right to help Iraq defend itself against ISIL in light of Syria’s unwillingness or inability to prevent ISIL from using its territory to carry out such attacks.

Both of these arguments are tenuous.

Current international law does not seem to endorse a right to pre-emptive self-defence in order to prevent a general threat from emerging into an armed attack. Claiming collective self-defence of Iraq faces the challenge that the airstrikes against ISIL in Syria, rather than being limited to necessary and proportional action to defend Iraq, seem to be aimed at eliminating the organisation.

Although ISIL poses a significant threat both for countries in the region and democracies in the West, it is not clear what declaring “war” on the organisation actually entails, nor is it clear that the airstrikes currently carried out in Syria are lawful under international law.

Of course, international law can change over time and it is possible that the action now being taken by States individually and collectively will give rise to a broader right to self-defence against terror groups such as ISIL.


Image source

Thomas Obel Hansen

US International University, Nairobi

Published Date
December 10, 2015