The Procedure of the UN Security Council, 4th Edition is available at Oxford University Press in the UK and USA. 

The Procedure of the UN Security
Council, 4th Edition

ISBN: 978-0-19-968529-5


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Updated on 13 September 2015


Section 12:   Communications


Self-defence under Article 51 invoked in cases related to individuals


On 7 September 2015, the representative of the United Kingdom wrote to the President of the Security Council to report pursuant to Article 51 of the Charter that his country “has undertaken military action in Syria against the so-called Islamic State in Iraq and the Levant (ISIL) in exercise of the inherent right of individual and collective self-defence.”  According to the letter, on 21 August 2015, United Kingdom armed forces “carried out a precision air strike against an ISIL vehicle in which a target known to be actively engaged in planning and directing imminent armed attacks against the United Kingdom was travelling.”  The letter affirmed that this air strike “was a necessary and proportionate exercise of the individual right of self-defence of the United Kingdom” (S/2015/688).   


This letter represents the first time that a lethal drone strike by one country against a suspected terrorist in another country has been reported to the Security Council as having been carried out pursuant to Article 51.  That article reads: 


“Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security.  Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.”  


The United Kingdom letter contained two different justifications:  First, as quoted above, the letter stated that the “target” in the ISIL vehicle was “known to be actively engaged in planning and directing imminent armed attacks against the United Kingdom”.  As a second justification, the letter underscored that “ISIL is engaged in an ongoing armed attack against Iraq, and therefore action against ISIL in Syria is lawful in the collective self-defence of Iraq.”


Attacks killing suspected terrorists in another country have been carried out by other governments but not reported to the Security Council as acts of self-defence in accordance with Article 51.  For example, in 2011, the United States Government announced that an American drone and jet strike in Yemen had targeted and killed the suspected terrorist Anwar al-Awlaki, an American citizen.  An American Justice Department memorandum was later released which concluded that the law authorizing force against al-Qaeda provided a legal basis for the killing of al-Awlaki, and the United States did not report the strike to the Security Council as an act of self-defence under Article 51.  It remains to be seen whether the United Kingdom letter of 7 September 2015 will influence future practice in this regard.


In one instance, the United States informed the Council of action it had taken against an individual in another country as an act of self-defence in accordance with Article 51, but this individual was captured, not killed.  By a letter dated 17 June 2014 to the Council President, the representative of the United States reported that her Government had captured in Libya Ahmed Abu Khattalah, who would be presented to a United States federal court for criminal prosecution for his role in the 2012 attacks against the American Mission and its personnel in Benghazi.  Stating that a “painstaking investigation” had determined that Abu Khattalah “continued to plan further armed attacks against United States persons”, the letter affirmed that his capture in Libya was “therefore necessary to prevent such armed attacks”, and was “taken in accordance with the United States’ inherent right of self-defence” (S/2014/417).


Other articles relating to reporting pursuant to Article 51 on this website include:

Letters citing Article 51 sent to the Council in 2014 and 2015

A historical overview of reporting pursuant to Article 51