Developments in international law: self-defence against imminent armed attack

TC Beirne Law Public Lecture Series
Professor Sarah Derrington and Senator the Honourable George Brandis QC

The TC Beirne School of Law and the University of Queensland were honoured on 11 April 2017 to host an important lecture by the Attorney-General for Australia, Senator the Honourable George Brandis QC. 

Download the audio of the lecture, or read the transcript

In this lecture the Attorney-General articulated the Australian government’s position on various rules of customary international law governing the use of armed force in self-defence. Customary international law develops through the general and consistent practice of States where that practice is accompanied by a sense, on the part of States, of international legal obligation or international legal entitlement (this second requirement for the existence of customary international law is often referred to as “opinio juris”). 

Evidence of such State practice and opinio juris can include, or be found in, general statements made or endorsed by senior State officials. This has been the consistent view of the International Court of Justice, expressed, for example, in its 1996 Nuclear Weapons Advisory Opinion.[1]  It is therefore a matter of considerable international legal significance when the First Law Officer of the Commonwealth of Australia articulates the Australian government’s understanding of the rules of customary international law that bind Australia. This is one important sense in which the Attorney-General’s lecture can be understood.[2] The international legal significance of such a lecture increases when it includes the endorsement and reaffirmation of other important statements made on behalf of other States such as the speech of the Attorney-General of the United Kingdom delivered on 11 January 2017.[3] 

In addition to the formal legal significance under international law of the Commonwealth Attorney-General’s lecture on 11 April 2017, the address given by Senator Brandis is also substantively significant for the important support it offers for the existing rules of customary international law regarding anticipatory self-defence and, in particular, the requirement that the use armed force in anticipatory self-defence must only occur where the anticipated armed attack is imminent. In re-affirming the imminence requirement, the Commonwealth Attorney-General, following the UK government’s position articulated, for example, on 11 January 2017, rejects the notion of pre-emptive self-defence in respect of threats of non-imminent armed attacks.  The Australian government’s reaffirmation of the established rules of international law regarding self-defence, albeit applied to new threats, is therefore to also be welcomed as it protects against the destabilising and dangerously permissive approaches to uses of armed force often associated with the so-called “doctrine of pre-emption”.

Senator Brandis refers in his lecture to various other important statements of international law including a 2012 journal article by Sir Daniel Bethlehem,[4] a speech given in 2016 by the Legal Adviser of the US Department of State, Mr Brian Egan,[5] the Chatham House Principles of International Law on the Use of Force in Self-Defence[6] and the Tallinn Manual.[7] The Attorney-General’s lecture should therefore also be considered in light of these resources.  Finally, it is important to note that the Attorney-General’s speech focused on the imminence requirement and did not seek to address all of the international legal requirements of the right to self-defence, such as the gravity threshold for the existence of an actual or threatened armed attack by non-State actors;[8] nor did the Attorney-General address other potential justifications under international law for the use of force.[9]


[1] Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Reports 1996, p 226 at pp 253-255, [64]-[70].

[2] Senator Brandis also refers, for example, to the “culture of justification” as articulated by the late South African scholar, Professor Etienne Mureinik.

[3] The text of the address given by the Attorney-General of the United Kingdom on 11 January 2017 is available at <>.

[4] Daniel Bethlehem, Self-Defense Against an Imminent or Actual Armed Attack by Non-State Actors (2012) 106 American Journal of International Law 770.

[5] Keynote Address: Brian Egan, Legal Adviser, US Department of State, 1 April 2016, Annual Meeting of the American Society of the International Law.  A video of this keynote address is available at <>.

[6] The Chatham House Principles of International Law on the Use of Force in Self-Defence (2006) 55 International and Comparative Law Quarterly 963.

[7] Michael N Schmitt (General Editor), Tallinn Manual 2.0 on the International Law Applicable to Cyber Operation, Cambridge University Press, Cambridge, 2017.

[8] Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America), Merits, Judgment, ICJ Reports 1986, p 14 at pp 101-104, [191]-[195]; Oil Platforms (Islamic Republic of Iran v United States of America), Judgment, ICJ Reports 2003, p 161 at [51], [63]-[64] and [72]; and the Chatham House Principles, note 6 above, at p 971 although note also the views expressed at p 966.

[9] The Attorney-General of the United Kingdom, for example, in his address on 11 January 2017 referred to uses of force justified on the grounds of so-called “Humanitarian Intervention”.  Necessity, as a circumstance precluding wrongfulness under the law of State responsibility, may possibly be invoked by States in relation to uses of force that do not violate the peremptory prohibition of aggression under international law.  See, for example, Roberto Ago’s Eighth Report on State Responsibility [1980] Yearbook of the International Law Commission, Volume II, Part 1, 13 at 39-51.

Last updated:
17 May 2017