Keeping the Ukraine-Russia Jus ad Bellum and Jus in Bello Issues Separate
In any situation of international armed conflict (IAC), such as that between Ukraine and Russia right now, two bodies of law necessarily come into sharp relief: The jus ad bellum, which deals with the “why” of the IAC (the legitimacy or otherwise of going to war); and the jus in bello, which is about the “how” (the lawful conduct of hostilities through compliance with the law of armed conflict (LOAC)).
The jus ad bellum in respect of Russia-Ukraine has been ably analyzed by Mike Schmitt, and deals with issues of national and collective self-defence, the UN Charter—especially Article 2(4), and the Article 51 “armed attack” threshold—and the legality or otherwise of “humanitarian intervention.” Traditionally, this assessment has been linked to key questions about lawful authority, right intention, reasonable hope of success, and proportionality as elaborated in the theological-ethical-legal “Just War” doctrine. The focus of these jus ad bellum assessments is political and military leaders. And jus ad bellum questions closely overlap with—but are nevertheless still separate from—the question of the crime of aggression. While a breach of the jus ad bellum and crime of aggression are not always co-present, with respect to Ukraine there is little doubt that Russia has perpetrated both a breach of the jus ad bellum and (as the UN General Assembly has affirmed) an act of aggression.
But Jus in Bello Focuses on Different Things…
The focus of the jus in bello, however, differs in several respects. For example, the jus in bello applies equally, at all times, to both the combatant parties (Ukraine and Russia) in their conduct of the armed conflict. There is no “higher” or differential level of potential culpability for jus in bello breaches on the aggressor State’s forces because they started the war; both belligerents’ forces are subject to the same rules and assessment standards. That is, the fact that one side is the clear aggressor does not mean we then assess that side’s jus in bello conduct differently—more critically—than the jus in bello conduct of the victim State’s forces. A war crime is a war crime, is a war crime.
Another difference is that where a jus ad bellum assessment tends to result in a single, holistic, integrated conclusion—the use of force was legitimate or it was not—the jus in bello operates through a series of ongoing, individual assessments of issues such as targeting, civilian and other protections, detention and internment, and person and object status. Interchangeably known as LOAC, international humanitarian law (IHL), or the law of war (although there are some subtle substantive differences that can be read into the label employed), this body of law governs the granular allegations we see emerging from Ukraine regarding artillery and rocket attacks on apartment buildings, targeting of infrastructure, and attacks against civilians.
Therefore We Do Need to Keep Jus ad Bellum and Jus in Bello Separate…
Consequently, the orthodox—and correct—view is that jus ad bellum and jus in bello assessments must be kept separate, so that neither contaminates the other. The US Law of War Manual, for example, affirms that “[a]s a general matter, jus in bello and jus ad bellum address different legal issues and should not be conflated” (§ 3.5.1). This is not to say that there are not interlinkages and co-dependencies between the two bodies of law—for example, the jus ad bellum concept of “right authority” does have some implications for jus in bello issues of command authority and responsibility. But on the whole, the two sets of rules are kept separate and—although the same facts might speak to both rulesets—assessed separately. There is a range of reasons that this is essential.
One reason to keep the two rule-sets separate is that LOAC assessments are relevant to everyone’s conduct—from rifleman to General, from a farmer taking up arms to a political leader, from computer operator to sniper. Jus ad bellum assessments, however, are concerned only with the conduct of those who “order” the use of force which triggers or expands the armed conflict, not with those who then go on to fight it.
Another reason to keep the two rulesets separate is that if the jus ad bellum were allowed to infect the jus in bello, there is a risk that either or both of the belligerent forces might allow their victimhood to infect their view of the opposing forces, and civilians, as being somehow less worthy of LOAC protection. This is also reflected in the fact that reciprocity in terms of positive LOAC compliance by all belligerents is a fundamental aim of LOAC; reciprocity in a jus ad bellum context is often understood more negatively—as a force operating against restraint—and is thus to be discouraged. Indeed restraint in response to a breach of jus ad bellum—such as when South Korea did not respond in kind when North Korea committed an armed attack by sinking the corvette ROKS Cheonan (with the loss of 46 sailors)—is often considered politically laudable.
A third reason to keep these two bodies of law as separate as we can is that the jus ad bellum and the jus in bello share some essential terminology. But those terms mean quite different things when employed within each ruleset. For example, assessing proportionality in analyses of national self-defense (which looks to correlations and correspondence—but not formal equivalency—between the attack suffered and the force planned or used in response), is a very different thing to assessing proportionality in LOAC contexts. In LOAC, proportionality (as expressed in AP I art 51(5)(b), for example) describes both a process and an outcome designed to deliver a judgment that the incidental death, injury, and damage expected to be caused to civilians and civilian objects from a specific attack, is not disproportionate to the anticipated military advantage (the legitimate military purposes to be achieved) that will flow from carrying out that attack.
Another shared, but differently nuanced, concept is “attack.” In jus ad bellum analyses, “armed attack” is a key threshold in that UN Charter Article 51 provides that when a State suffers an “armed attack,” its right of national self-defence is activated. In LOAC, an “attack” is an act of “violence against the adversary, whether in offence or in defence.” Whilst the same fact situation may indeed speak to both thresholds—the initial Russian fires against Ukrainian air defence capabilities, for example, was both a jus ad bellum armed attack and a LOAC attack—these two concepts differ in a number of ways.
First, the jus ad bellum concept of armed attack carries with it a requirement of gravity—expressed often in terms of scale and effect—that is absent from the LOAC concept; indeed, a single round fired from a soldier’s rifle is a LOAC attack. Second, the main purpose of the armed attack concept is to act as a threshold which triggers the victim State’s right to use force in national self-defence. By contrast the main purpose of the LOAC concept of attack is to enliven certain LOAC obligations in the perpetrator—obligations that precede the attack (do a proportionality assessment), endure during the attack (discontinue if it looks like there might be more collateral damage than expected), and continue after the attack (such as, if there is a suspicion as to war crimes, to investigate). Third, although the same fact situation often speaks to both concepts of attack, not all armed attacks are LOAC attacks. Take for example the insertion of a State A infantry company crossing the border into State B territory. The company is not disguising its status as a State A military unit (that is, they are not “little green men”), but its presence is not discovered by State B until the company has dug in. Not a single shot has been fired, and no kinetic or cyber force was used. This is most certainly an armed attack and might also be an act of aggression (UNGA Res. 3314 (XXIX) definition art. 3(a)); but it is not a LOAC attack.
Although Keeping Them Separate Can Present Some Challenging Issues…
This does not mean that there are no challenges in keeping the two bodies of law separate, and separately assessed. As has been noted previously (here, for example) the threshold of military activity required under LOAC for an IAC—as described in Common Article 2 of the 1949 Geneva Conventions—is astonishingly low. As is classically stated in the Pictet Commentary, LOAC is triggered by
Any difference arising between two States and leading to the intervention of armed forces is an armed conflict within the meaning of Article 2…. It makes no difference how long the conflict lasts, or how much slaughter takes place. The respect due to human personality is not measured by the number of victims.
As noted above, the threshold for an armed attack—a jus ad bellum question—is undoubtedly higher than this, and does not include (although this is contested, and also implicates the “no gap” approach to use of force analysis) “mere frontier incidents” (Paramilitaries case, § 195). It is, as a matter of law, possible for the facts on the ground to indicate that Common Article 2 has been triggered in a situation where the jus ad bellum armed attack threshold has not. In some respects, this is a consequence of the different priorities these rulesets encapsulate. The jus ad bellum is ultimately preventively-focused, while LOAC is protectively-focussed (and simultaneously also mission achievement-focused). Likewise, the spectrum of thresholds for an act of aggression listed in Articles 1 through 3 of the definition in UNGA Res. 3314 (XXIX) has parallels with both the Common Article 2 IAC threshold and the jus ad bellum threat of force, use of force, and armed attack thresholds. We must be vigilant in using LOAC thresholds for LOAC assessments, and jus ad bellum thresholds for such macro-use of force assessments.
Another challenge to keeping jus ad bellum and jus in bello assessments separate is the idea of a partial effect-based “double trigger” for LOAC attacks (here, for example). This is essentially an assessment that an individual attack being planned and assessed against LOAC as to lawfulness, may also still need to pass a broader jus ad bellum test as well. This question as to blurred thresholds has also arisen in relation to (national) “self-defence targeting” (here, as Geoffrey Corn notes) and the targeting of satellites (here, as Hitoshi Nasu notes). This concept of a double jus ad bellum–jus in bello trigger, however, is different to—and must be kept separate from—the entirely LOAC referenced approach of assessing the expected military objective to be achieved from an attack on a “campaign” (as opposed to single tactical attack) level. As Australia and others have declared in relation to AP I art 51(5)(b), “references to the “military advantage” are intended to mean the advantage anticipated from the military attack considered as a whole and not only from isolated or particular parts of that attack and that the term “military advantage” involves a variety of considerations including the security of attacking forces.”
Conclusion
Ultimately, jus ad bellum and jus in bello analyses often rely—at least initially—upon overlapping matrices of conduct, actor, and effect. But it is essential to always recall that these two rulesets serve different purposes, and employ different thresholds, assessment concepts, and methodologies—although these different concepts can sometimes share the same label. And in the current Ukraine-Russia situation, where it is so clear who the aggressor is, it is critical that we rigorously police the borders between these two bodies of law so that we do not allow our conclusions as to jus ad bellum culpability to contaminate our impartiality in terms of holding both sides properly to account against the same jus in bello standards.
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Rob McLaughlin is a Professor of Military and Security Law at UNSW Canberra and a Professor of International Law at Australian National Centre for Ocean Research and Security.
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