On 21 September 2013, gunmen stormed Nairobi’s Westgate mall, randomly firing at people and taking hostages. The siege lasted four days. At least 67 people are known to have died and more than 200 were injured. Somalia-based Al-Shabaab claimed responsibility for the attack. On 24 September 2013, while declaring the end of the siege, Kenyan President Uhuru Kenyatta promised full accountability for the attack.

After a four-day stand-off, security forces succeeded in ending the siege, killing five gunmen and apprehending several others. The question thus arises whether similar law enforcement action will suffice to ward off future attacks and address the overall threat al-Shabaab poses to Kenya and the region.

Based in Somalia, al-Shabaab is believed to have approximately 5000 fighters, with foreign jihadists reportedly traveling to the country to join the group. Despite having been forced out of most urban areas, al-Shabaab remains in control of most of southern and central Somalia. In February 2012, its leader, Ahmed Godane, pledged obedience to al-Qaeda head Ayman al-Zawahiri. Moreover, the group has been recruiting US and European citizens.

It is thus reasonable to assume that law enforcement alone will not eradicate the danger al-Shabaab poses. The Kenyan government may consider using military force against the group in exercise of its right to self-defence. This would not be the first time Kenya took defensive action against al-Shabaab. In October 2011, the Kenyan military entered Somali territory to fight the militants. In a letter to the Security Council, the Kenyan Permanent Representative reported that “Kenya, (…), has, after the latest direct attacks on Kenyan territory and the accompanying loss of life and kidnappings of Kenyans and foreign nationals by the Al-Shabaab terrorists, decided to undertake remedial and pre-emptive action”. 

After 9/11, the Security Council implicitly recognized that self-defence could be used against terrorist attacks. Since then, it is increasingly accepted that the right of self-defence, as enshrined in Article 51 of the UN Charter, can be invoked against non-state actors, as long as the customary law requirements of necessity and proportionality are met (see Chapter 10 of my book on this topic).

The question then arises whether the mall siege amounts to an armed attack, triggering the exercise of self-defence. The siege lasted four days, resulted in a high death toll, caused widespread injury and considerable property damage. Such attacks are generally accepted as reaching the threshold of armed attacks (see Chapter 3 of Tom Ruys’ book on this topic).

That consideration alone, however, is not enough to invoke the right of self-defence. The principle of necessity also requires that there is a sense of emergency (immediacy), which makes defensive use of force urgent and inevitable. If the threat can be neutralized through other means, the exercise of self-defence cannot be justified. Continue reading →