Guest Post: Unit Self-Defence

by Ian Henderson and Bryan Cavanagh

[Ian Henderson is a group captain in the Royal Australian Air Force and is currently posted as the Director Military Law Centre and Deputy-Director Asia-Pacific Centre for Military Law. Bryan Cavanagh is a squadron leader in the Royal Australian Air Force and is currently posted as a legal training officer at the Military Law Centre and Asia-Pacific Centre for Military Law. This note was written in their personal capacities and does not necessarily represent the views of the Australian Government or the Australian Department of Defence. This is the third in a four-part series. The first post can be found here (along with a response here), the second here and the third here.]

In this final post, we briefly discuss the concept of unit self-defence. Unit self-defence is a term used in rules of engagement (ROE) and can be defined as ‘the right of unit commanders to defend their unit, or others units of their nation, and other specified units against hostile acts or hostile intent’ (see the annex D of the San Remo ROE Handbook). In some militaries, along with being described as a right, it is also described as an obligation (see CJCSI 3131.01B, U.S Standing Rules of Engagement). In other words, a commander is positively required to act in unit self-defence and can be held accountable for not doing so.

In our view, and with due respect to those who have argued that unit self-defence has an independent legal basis, the better approach is to view unit self-defence purely as an ROE concept (much like the terms observed indirect fire and unobserved indirect fire) that has underlying law and legal consequences but is not a legal term in and of itself. Considered that way, unit self-defence can be thought of as:

a) a form of delegated authority from the national command chain of a State to exercise a State’s right of national self-defence in limited circumstances and in a constrained fashion;

b) a reminder of the criminal law authority to act in self-defence to protect oneself and protect others, (recalling that the criminal law concept of self-defence allows a person to not only defend his or herself, but also to defend another person where the person to be aided is in a situation where the law would allow that person to act in self-defence); and

c) an order or command to use military force when certain ‘triggers’ are present.

We believe deconstructing unit self-defence in this way is helpful as it focuses on the legal basis for any given use force (or non-use of force if a commander failed to act in unit self-defence) based on the jurisdiction in which the issue would be litigated. For example, if the matter is being litigated in the International Court of Justice, it will be the State that is the party. As such, the legal issue is likely to be whether the State had a right to use force. Conversely, in a criminal proceeding in a domestic court or international tribunal, it will be individual military members who are being prosecuted; and so, combatant’s privilege aside, the issue is more likely to be whether the individual had the right to use force. And finally, through ROE a commander (or for that matter, any other military member) can be ordered to use force (and held accountable for not doing so) where the circumstances are such that under the law of self-defence they would be legally permitted but not compelled to use force in defence of another.

We are very thankful to the editors of OpinioJuris for giving us this opportunity, as well as for the useful comments and discussion from the readers.

5 Responses

  1. “a” makes sense, because writers have recognized that a military unit or force in State A that comes under an armed attack from a NSA or other state has a UN art. 51 (and CIL) rights of self-defense — without the consent of the host state A and without state A having any involvement or being unwilling or unable to stop the armed attacks. See my earlier draft article on self-defense targetings near the end of the draft — I have added to the draft but the editors do not want me to post the changes. If anyone “out there” has some useful additional citations, please leet me know [please post here].
    BUT “hostile intent”? Surely that goes to far.

  2. “a” makes sense, esp. b/c writers have recognized that a military unit or force within another country (State A) has a right under UN art. 51 and/or CIL to engage in responsive measures of self-defense against a NSA or other state armed attack even though State A is not involved, is not unwilling, etc., etc. see my draft article near the end —
    I would appreciate additional citiations for the footnotes.
    BUT “hostile intent”? Surely this goes too fr.

  3. Jordan,

    Thanks for your comment and your continued engagement with this mini-symposium on our book chapter. We look forward to reading your article. Do you discuss using force to defend the UAV itself?

  4. no — any thoughts?

  5. I have done more research into “unit self-defense,” and find that an article by Dale Stephens in 45 Naval L. Rev. (1998) seems to be well-cited — and in a but see cite by Mary Ellen (39 Devner J. at 598-99

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