Kenya Invades Somalia Relying on the Right to Self-Defence

On 16th October 2011, Kenya launched ground troops deep into Somali territory in “Operation Protect the Nation”. In order to justify its actions, the Kenyan government invoked the right to self-defence against Al-Shabaab, a terrorist group based in Somalia. The Kenyan invasion of Somalia demonstrates how the fight against terrorism continues to test the boundaries of the law of self-defence.

The Kenyan Invasion of Somalia

Al-Shabaab is an armed Islamist group that controls much of southern and central Somalia. The Kenyan government alleges that Al-Shabaab has carried out border attacks and has kidnapped, and in some cases killed, Western tourists and aid workers in 9 separate incidents on Kenyan territory last year. The group is also said to have accentuated the human suffering caused by the East African famine by endangering and denying access to aid agencies working in Somalia.

Since mid-October 2011, Kenya has sent 1,600 ground troops across the border into Somalia and carried out airstrikes against Al-Shabaab. At a press conference on the eve of the invasion, the Kenyan Internal Security Minister explained that the right to self-defence justified Kenya’s actions:
“The Kenyan government is taking robust measures to protect and preserve the integrity of the country by invoking Article 51 of the UN Charter.”

The President of Somalia initially rejected this justification, stating “Somalia’s government and its people will not allow forces entering its soil without prior agreement.” However, in a Somali-Kenyan joint communiqué of 31 October 2011, the Somali government gave credence to Kenya’s justification by accepting that:

“Kenya’s security operation inside Somalia is aimed at eliminating the threat posed by Al-Shabaab to Kenya’s national security and economic well-being, and is based on the legitimate right to self-defence under Article 51 of the UN Charter.”

The Right to Self-Defence in International Law

Under Article 51 of the United Nations (“UN”) Charter and in customary international law, the right of States to use force in self-defence is exceptional and may only be used:

in response to an armed attack;
which is of sufficient gravity;
and if the force used is proportionate to the armed attack and necessary to respond to it.

Kenya’s invasion of Somalia raises questions in respect of each of the above conditions.

Armed Attack

There is no doubt that the right to resort to force in self-defence exists “in the case of an armed attack by one State against another State” (Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, 2004 ICJ Rep 136, 194). It is less clear whether a State may rely on the right of self-defence to use force in response to an attack by a non-State armed group based in the territory of another State. The International Court of Justice (“ICJ” or the “Court”) has not yet accepted this application of the right. Article 51 of the UN Charter has been interpreted by the Court to require that an armed attack must be attributable to a State. As a result, Kenya would, ordinarily, have to establish that Somalia had effective control over Al-Shabaab’s activities in order to justify its recent invasion of Somalia.

In the aftermath of the 11 September 2001 terrorist attacks against the United States (“9/11”), the law of self-defence arguably changed to allow States to confront terrorist safe-havens. States and international organisations ostensibly accepted that Al-Qaeda had carried out an armed attack against the United States. Following 9/11, the UN Security Council affirmed the right to self-defence in Resolutions 1368 and 1373, and the NATO Council invoked the right to self-defence following an “armed attack” by reference to Article 5 of the NATO Treaty. The States involved in, and supportive of, the United States’ invasion of Afghanistan relied on the right to self-defence without seeking to attribute Al-Qaeda’s acts to the Taliban or Afghan State. It is unlikely that the Taliban possessed sufficient effective control over Al-Qaeda to establish legal attribution, despite the connection between the two organisations.

Yet, there must be some limits on the use of self-defence against non-State armed groups, otherwise the mere presence of terrorists within a State could, conceivably, allow recourse to force. It has been argued that the right to self-defence arises if a State is “unwilling or unable” to counter the threat of terrorists operating within its borders. This appears to be the rationale behind international support for the Kenyan invasion, as well as for the drone strikes taking place in Pakistan and Yemen. This argument has provoked criticism on the basis that it turns Somalia’s vulnerability into an authorisation to attack its territory, further undermining Somali sovereignty. On the other hand, Al-Shabaab is said to be in belligerent occupation of large parts of Somali territory, over which the interim Somali government has no control. This fact may attenuate the State attribution requirement in the law of self-defence as it changes the practical impact of the Kenyan invasion on Somalia’s de jure government.


The nine incidents cited by Kenya are unlikely individually to constitute “the most grave forms of the use of force (those constituting an armed attack)” (Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), [1986] ICJ Rep. 14, paragraph 191). They are even less likely to do so if armed attacks by non-State armed groups must meet a higher threshold of gravity, as suggested by the ICJ in Armed Activities in the Congo ([2005] ICJ Rep. 116, paragraph 147). The proposition that several minor incidents can be aggregated to constitute one armed attack is unlikely to assist Kenya. The nine incidents complained of were small-scale, disparate and several were denied by Al-Shabaab.

Proportionate and Necessary Measures

Kenyan forces have ousted Al-Shabaab from its southern strongholds and occupied several towns in Somalia. However, in the Armed Activities in the Congo case, the ICJ stated:

“The Court cannot fail to observe, however, that the taking of airports and towns many hundreds of kilometres from Uganda’s border would not seem proportionate to the series of transborder attacks it claimed had given rise to the right of self-defence, nor to be necessary to that end.”

The Future for Somalia and the Law of Self-Defence

More than ten years after the terrorist attacks of 9/11, States continue to claim that the law of self-defence permits them to use force in the territory of States that provide safe-havens for terrorists. However, these claims regarding the state of contemporary international law have yet to be expressly addressed or validated by the ICJ. Notwithstanding the Court’s reticence to expound on this matter, the growing trend towards asymmetric conflict suggests that a State’s right of self-defence against non-State actors is an issue likely to remain in sharp focus.