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The Legality of Armed Intervention

Image © Exeter Express and Echo

About The Author

Francesca Norris (Solicitor Outreach)

Francesca is a trainee solicitor at a leading national firm, having undertaken the GDL subsequent to graduating with a Combined Honours in Arts from Durham. Her primary areas of interest are human rights, public law, clinical negligence, and criminal law.

On Friday 26th September, MPs in the House of Commons voted by 524 to 43 to sanction UK air strikes against Islamic State targets in Iraq. Yet again, images of RAF Tornadoes fill our newspapers and television screens as British military forces find themselves put to work in a war-torn Middle-Eastern country: a familiar position by now, following the multitude of British military operations in the region since 2001. This article examines the grounds upon which the UK, the US and their allies are legally able to commence such missions, and why the legal positions regarding strikes in Iraq and Syria may be different.

The issue of when it is appropriate for one state to intervene in another state’s domestic or defensive policy is emotive, and discussions tend to be tainted by the socio-political implications of intervention versus non-intervention in each particular case. Nowhere are such complications more pertinent than in the current situation regarding the Middle East. Following the 9/11 terrorist attacks, the invasion of, firstly, Afghanistan in 2001 and then Iraq in 2003 entrenched Britain, the US and their allies firmly in Middle Eastern social and political struggles. Rather than the promised Enduring Freedom (the name given to the USs operation against the then-ruling Taliban regime and terrorist faction al-Qaeda in Afghanistan), the region has lurched from one crisis to another, culminating in a fractured and fragmented region. This region has been defined by the prevalence of power vacuums which contributed indirectly to last years horrifying events in Syria and arguably directly to the threat currently posed both in the region and around the world by self-appointed caliphate, Islamic State (IS).

The General Legal Position

Simplistically, as common sense would suggest, the general position under international law is that one state cannot drop bombs on another state’s territory, as this violates the latter’s political independence and sovereignty. Article 2(4) of the Charter of the United Nations prohibits the threat or use of force against territorial integrity or political independence of any statewhilst a states freedom of self-governance is enshrined in Article 2(7), which sets out that:

Nothing contained in the present Charter shall authorize the United Nations to intervene in matters which are essentially within the domestic jurisdiction of any state

Further, although Article 2(7) does not directly concern the relations between individual states, but the relations between the UN itself and its constituent member-states, the UN General Assembly has often adopted a negative attitude towards interventions by individual states. GA Resolution 2625 (XXV) states that:

No state or group of states has the right to intervene, directly or indirectly, for any reason whatever, in the internal affairs of any other state.

There are a number of defined and accepted exceptions to the prohibition on the threat or use of force by one state within the territory of another, most commonly either a United Nations Security Council Resolution under Chapter VII of the UN Charter sanctioning such measures, or alternatively the invocation of a state’s right to self-defence as enshrined in Article 51 of the UN Charter. This article will explore these issues in more detail later.  However, with regard to the situation in Iraq, it must first be examined whether Western military intervention to help defeat ISIS engages the UN Charter at all.

On what grounds is intervention in Iraq legal?

Put simply, the air strikes in Iraq are legal because Iraq have asked for them.  It was first reported in June 2014 that Iraqi Prime Minister, Nouri al-Maliki had requested assistance from the US in confronting the threat posed by IS after they seized control of major Iraqi cities. Article 20 of the International Law Commission’s (“ILC”) Articles on the Responsibility of States for Internationally Wrongful Acts sets out that ‘[v]alid consent by a State to the commission of a given act by another State precedes the wrongfulness of that act in relation to the former State to the extent that the act remains within the limits of that consent'. The UK, the US and their allies can therefore legally commence airstrikes against IS in Iraq on the basis that Iraq have consented to such strikes; as the Iraqi government have authorised the action, no authorisation from the UN Security Council (under Chapter VII of the Charter, as set out above) is required for the strikes to be lawful.

However, Iraqi authorisation can only extend to the situation within Iraq itself. The threat presented by Islamic State is a cross-border threat, and any use of military force that extends past the Iraqi borders would arguably fall foul of the ILC Article 20 provision, and therefore the UN Charter, as it would transcend the authority that the Iraqi government was legally able to provide.  As such, airstrikes in other countries where IS have a strong foothold could prove more problematic.


The situation in Syria is complex.  To begin with, Syrian President Bashar al-Assad has not directly requested Western military assistance in combating the threat posed by Islamic StateEven in the event that al-Assad did request intervention from Western countries, it would be politically challenging for the UK or US to “team up” with the Assad regime following the alleged atrocities it has committed against Syria’s own citizens, as a House of Commons Library Paper published in September 2014 pointed out.

Use of force on Syrian territory without authority given by the Syrian government would therefore seem to contravene obligations under the UN Charter, amounting to a breach of Articles 2(4) and 2(7) set out above. Arguably, the threat posed by Islamic State is not ‘essentially within the domestic jurisdiction’ of Iraq or Syria per Article 2(7): it is the group’s cross-border capacity that gives it the prominence and power that it has so far amassed. There can be no argument that the threat posed by Islamic State is not confined to within the borders of Iraq or Syria, as the group have allegedly set out a five-year territorial expansion plan and the brutal executions we have already witnessed of both Western and Middle-Eastern hostages demonstrate that IS intend to intimidate, threaten, terrorise, and ultimately destroy those that do not subscribe to their particular ideological outlook. However, even setting aside Article 2(7), Article 2(4) would still stand to prohibit the use of force within the Syrian borders.

A UN Security Council Resolution is also unlikely to be forthcoming: Russia, an ally of Syria since the Cold War, has made it clear that it will veto any attempt to pass such a resolution. Further, China has also repeatedly vetoed resolutions threatening military and economic sanctions in Syria on the basis that such measures would constitute an attempt to force the Assad regime out of government.

The only option left available to states attempting to justify intervention in Syria is the right of self-defence, which can be exercised without the authority of a UN Security Council resolution.  Article 51 of the UN Charter states that ‘nothing in the present Charter shall impair the inherent right of individual and collective self-defence if an armed attack occurs’.

Arguably, the very prospect of Islamic State attacks on the US or its allies, including the UK, falls under Article 51 because the article does not specify that any such attacks must be made by state actors.  Although the International Court of Justice (”ICJ”) has previously held that Article 51 recognises the right of self-defence only in the case of an armed attack by one State against another state, dissenting opinion from within the Court itself stated that nothing within the text of Article 51 stipulated as suchRegardless, the ICJ does not possess authority to amend or narrowly interpret the UN Charter so as to alter the Charter’s meaning. Furthermore, since the international community unitedly sanctioned military operations against al-Qaeda in Afghanistan in 1998 and 2001, Security Council Resolutions 1368 and 1373 recognise the right of self-defence as it relates to a terrorist threat, not necessarily a threat posed by a state.

Such armed attacks can be deemed to be already underway by Islamic State against the US and its allies if one adopts the viewpoint of Judge Humphrey Waldock, formerly of the ICJ, who stated that:

Where there is convincing evidence not merely of threats and potential danger, but of an attack being actually mounted, then an armed attack may be deemed to have begun to occur, though it has not passed the frontier.

David Cameron has spoken about the threat posed to the UK if IS succeed in establishing a widespread regime in the Middle East, and whether or not such a threat is as concrete and imminent as is made out. Given this, the narrative of the threat could, admittedly at quite a push, be invoked as justification for airstrikes in Syria on the grounds of self-defence.

Indeed, this argument for pre-emptive self-defence appears to form at least part of the US governments justification for their airstrikes in Syria. In a letter to UN Secretary-General Ban Ki-Moon, US Ambassador to the UN, Samantha Power set out that US action against the Khorason terrorist organisation in Syria was necessary in order to ‘address terrorist threats they pose to the United States and our partners and allies’, and as such was ‘in accordance with the inherent right of individual and collective self-defense [sic], as reflected in Article 51 of the UN Charter’. However, the doctrine of pre-emptive self-defence generally garners little support in the international community, and basing such a justification on non-imminent threats from non-state actors is tenuous indeed.

Nevertheless, the US invoke another limb of the “self-defence” justification to support Western military intervention against IS in Syria. Power’s letter also asserts that US action is justified on the grounds of collective self-defence; military operations in Syria are underway ‘in order to eliminate the ongoing ISIL threat to Iraq, including by protecting Iraqi citizens from further attacks and by enabling Iraqi forces to regain control of Iraq’s borders’. Thus, Iraq’s own right to self-defence can come into play on the international stage by virtue of the provisions of Article 51 as outlined above:

Iraq can invoke its right to self-defence under the UN Charter, and authorise the US to help it fulfil this right, because ISIS’s attacks are not purely internal… there must be an international dimension and given that ISIS’s main apparatus is in Syria, an apparatus from which it launches its attacks on Iraq, from which it mobilises fighters and garners its resources, this condition is sufficiently met.

In other words, because Islamic State attacks Iraq from Syria, and Iraq has requested international assistance in combatting Islamic State threats, airstrikes on Syrian targets could be legitimated by virtue of Iraq’s own right to self-defence.

Necessary and Proportionate?

Whether the US and UK were to invoke their individual right to pre-emptive self-defence, or the rights of Iraq to seek their assistance via the doctrine of collective self-defence, additional conditions must be met to justify military action in Syria.  Not only must there be at least some evidence of an actual and imminent armed attack against either the Western allies themselves or against Iraq, but that attack must be significant enough to warrant the corresponding military response. Given the territorial gains made by IS across Syria and the reports of the displacement and deaths of civilians across the country, this is unlikely to prove too controversial. Finally, response would have to be both necessary and proportionate. Ambassador Power specifically held that the US action is so, and it has been argued that anything less than the use of military force against IS ‘will only help the jihadist group expand its gains’, and that due to the inaction of the Syrian government, that military force must come from outside the country. 

Indeed, on 23rd September Ban Ki-Moon went some way to justifying the US airstrikes, stating at a press conference:

I’m aware that today’s strikes were not carried out at the direct request of the Syrian government but I note that the government was informed beforehand. I also note that the strikes took place in areas no longer under the effective control of that government. It is undeniable and the subject of broad international consensus that these extremist groups pose an immediate threat to international peace and security.


Iraq’s right to defend itself against the threat posed by IS, and to request assistance in doing so, is undisputed.  Extension of such intervention into Syria, however, strays into murkier legal territory. It remains to be seen whether the UK will join the US in strikes against IS targets in Syria. However, David Cameron has certainly left open the possibility of doing so, stating that he believes there to be a legal basis for extending airstrikes into Syria and providing for the possibility of the UK entering into urgent action in Syria without further consultation with parliament.

Assurances have been quick from both Barack Obama and David Cameron that there will be ‘no boots on the ground, and that military intervention in Iraq and Syria will not mean returning armed forces to the region so soon after the last Western forces have withdrawn from Iraq. Despite this, both governments, together with an ever increasing group of Western allies now including Australia and Canada, appear to be reacting to a fresh form of terrorist threat by pursuing fresh tactics of military intervention during the ongoing crisis in the Middle East.

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Tagged: Anti-Terror, Armed Conflict, International Law

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