US Strikes against Syria and the Implications for the Jus ad Bellum

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The blogosphere is abuzz with reactions to the U.S. strikes against Syria. My guess is that most international lawyers will agree with Marko Milanovic that the strikes were unlawful. Article 2(4) of the Charter prohibits the use of force by one state against another, except in self-defense or with the UN Security Council’s authorization. Neither exception seems to apply here. Moreover, although some have argued that international law also recognizes (or is in the process of recognizing) an exception for humanitarian interventions, that view is not widely endorsed. In any event, it would not obviously apply in Syria. Even Harold Koh — who has articulated one of the best justifications for unilateral humanitarian interventions — has recognized that “[i]t is too early to judge” whether the Syria strikes are lawful. In particular, it is not clear that the strikes “would demonstrably improve the humanitarian situation” in Syria.

My goal in this post is not to advance a different position on the law. It is instead to examine the implications of the U.S. action for the broader legal order.

A. Supporting the Prohibition of Chemical Weapons

Chemical weapons are not the only means with which the Assad government has committed atrocities, but they are a particularly barbaric and indiscriminate means. Assad’s repeat use of them, with apparent impunity, has weakened the absolute prohibition of chemical weapons — and with it, international humanitarian law (IHL) more generally. Those who are not steeped in international law inevitably interpret this fact pattern to mean that, IHL notwithstanding, anything goes in wartime, at least for those who have the right allies.

The U.S. strikes were intended to convey a different message – to show that the world is willing to enforce, however imperfectly and inconsistently, the prohibition of chemical weapons. To be sure, the humanitarian crisis in Syria will almost certainly continue. The point was not to address that crisis as a whole but rather to say that some things are never permissible, even in wartime. Indeed, most states that have expressly commented on the incident have suggested that they, too, view the strikes as appropriate. As such, the strikes are likely to have the effect of bolstering a prohibition that had been deteriorating.

B. Deteriorating the Article 2(4) Prohibition?

But what of the prohibition in Article 2(4)? Wouldn’t the same argument suggest that the strikes will undercut this, even more fundamental legal norm? Maybe but not necessarily. There is no reason to believe that states are less committed to Article 2(4) now than they were before the strikes. Instead, there’s reason to think that states are committed both to Article 2(4) and to the prohibition of chemical weapons — and that, for a variety of reasons, the latter trumped the former in this instance.

Moreover, there are precedents of states taking forcible reprisals without diminishing the salience of Article 2(4). The most well-known example is the U.S. raid on Baghdad in 1993, in response to evidence that Saddam Hussein tried to assassinate U.S. President George H.W. Bush on a trip to Kuwait. There too, the United States acted both to condemn the breach of a basic international legal norm — the attempted assassination of a foreign head of state — and to deter its recurrence. And there too, most states responded with silence or mild support. The effect was not to tolerate more reprisals across the board but rather to treat the Baghdad strikes as a one-off incident for addressing conduct that, if not deterred, could be destabilizing. Of course, the more states use forcible reprisals, the harder it is to treat them as one-off blips; the more they start looking like an uptick in states’ tolerance for unilateral force.

C. Mitigating Measures

The question, then, is how to replicate the Baghdad experience and mitigate the potential damage of the Syria strikes to Article 2(4). Some have called on the United States to present a legal justification for the strikes — for example, to make an expansive claim on defensive force or endorse a right to intervene unilaterally for humanitarian ends. Obtaining that kind of legal justification might serve certain interests that are associated with the rule of law, like transparency and the articulation of generally applicable legal standards. But it would also help diminish Article 2(4). It would mean advancing a novel legal claim to permit more unilateral force. Even if other states do not accept that claim at the moment, they or the United States could more easily invoke it to justify future actions. After all, the United States would have said that such actions are, in its view, lawful.

At the same time, just ignoring the jus ad bellum risks conveying a total disregard for the law. It risks suggesting that the United States does not view the jus ad bellum, and maybe international law more generally, as normatively relevant in the global order. That risk is heightened in the current political climate because other actions by the Trump administration arguably suggest the same.

What the United States should do, then, is underscore its overall commitment to and investment in the jus ad bellum. It could do this in any number of ways, including by issuing a presidential statement about the importance of Article 2(4) and of responding to security challenges through the Security Council. Such a statement might seem disingenuous at the moment, but it would serve an important signaling function, especially if it is backed up by concrete action going forward. The counterintuitive point is that, in the face of violating the black-letter law on the use of force, the United States ought to take advantage of this opportunity to endorse it.

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Adil Haque says

April 8, 2017

Hi Monica,

Sorry, just so I'm clear, is your conclusion that the U.S. should *not* offer a legal justification for the strikes, but *instead* issue a general statement about the importance of Article 2(4) and of responding to security challenges through the Security Council? Or that it should do both?



F. Cerqueira Alves says

April 8, 2017

Thank you Monica.

Several scholars have already raised the following: does the Charter exhaust the regulation of the use of force? With this in mind, I would recall your reference to forcible reprisals. This is not the first case where forcible reprisals are not consistently condemned by members of the international community. Actually, public reactions, aside from Russia, seem to suggest a different (opposite) direction in this case. While the action was taken outside a framework of collective reaction, the clearly punitive statements of US agents seem to point towards reprisals rather than humanitarian interventions. While the classic framework of the use of force and its exceptions as stated by Marko in this very blog today is hardly questionable, I believe the matter can deserve further reflection specially considering the absence of a hierarchy of sources in International Law (treaty v. customary law).


jurist says

April 8, 2017

I like this argument, because it helps bridge an unhealthy gap between what is very settled law (Article 2(4) of the Charter) and the gut reaction of non lawyers in Western democracies.
But this analysis, and other analysis I have read here in EJIL does not adequately address the way this looks from a non-US/Western nation perspective. Do policy makers and lawyers in places like Russia view this as a jettisoning of 2(4)? Do people who believe, honestly, Russian and Syrian claims that there is not enough evidence to show that the Asad regime was responsible for the chemical attacks, now consider the US and other Western democracies fair game and the UNSC as an unnecessary impediment to use of force?

Monica Hakimi says

April 8, 2017

Hi Adil,

Thanks for the question. I think the United States should issue a bland statement supporting the jus ad bellum but should not try to present a legal justification for the strikes. Any legal justification would be novel and a stretch -- and, in my view, would increase the risk of "opening the door" in future cases (especially because several other states have already endorsed the strikes).

I also think that, going forward, the United States should actually act like the Charter is relevant.


Veronika Bilkova says

April 8, 2017

Dear Monica,
thank you very much for this post which suggests a positive, and optimistic, interpretation of the current events. Indeed, if the prohibition of chemical weapons got strengthened and the prohibition of the use of force did not get weakened, we would end up with a good outcome. It could then be argued that sometimes, ex iniuria bonum oritur, i.e. that even an unlawful acts can bring something good.

Whether this will happen depends, as you rightly say, on various factors, one of them being the legal position that the US is to take now. Equally important will be the assessment provided by other countries (so far, the reactions are rather mixed) and the way in which similar situations will be dealt with in future.

As I wrote earlier, I am not sure the rule prohibiting chemical weapons is truly (legally) at risk. To my best knowledge, apart from Syria, only two other States (Israel and Saudi Arabia) are suspected of having used chemical substances /not even qualifying as chemical weapons under CWC/ against civilians. The violations of the rule are thus quite limited and no one seems to claim that this rule should be abolished or that some exceptions to it should be accepted. You are nonetheless right that highly visible, albeit sporadic, instances of a violation of a rule which remain unpunished, may weaken the trust in the rule and, in fact, in international law as such. And that an action in support of such a rule, even if unilateral and unlawful, may help re-establish this trust.

So far, as Jurist notes above, the assessment of the US actions is not uniform. Some opt for the assessment along the lines you suggest, seeing in the strikes the beginning of a new era in which the international community, or some parts of it, will finally make it sure that, to use your words, “some things are never permissible”. Others take a less benign view, arguing that the action was premature, that it pursued other aims or that there is an inconsistency in the US approach indicating that the use of chemical weapons/substances only matters in some instances. If the US attack is to have the positive impact you describe, the latter allegations will have to be addressed and, to the extent possible, refuted.

As to Article 2/4 of the UN Charter, I am afraid you may be, for once, too optimistic to believe that the previous instances of unilateral use of force have remained without impact and that the salience of Article 2/4 has not been diminished. It is true that some of these instances did not bring an immediate reaction. Yet, this does not mean that they did not contribute to the weakening of the rule and, again, to the weakening of the general trust in the rule and in international law.

This time, the situation is made worse by States, and scholars, justifying their acts by sometimes very original legal constructions that expressly seek to change the existing regulation. And also by some States claiming that they are the ones – and the only ones – with the right to create new rules or to decide when the common rules do not apply in a sui generis case.

So far, the US strike seems to fall under this strand – further undermining the 2/4 prohibition. I am not sure that a statement expressing support to the Charter system could really mitigate this. But you are right that such a statement could not do much (more) harm and that the US simply stating it upholds the 2/4 prohibition, rather than trying to justify its action by yet another original legal construction, would probably be the best way of addressing this situation.

Alexandros Bakos says

April 8, 2017

Dear F. Cerqueira Alves,

I would like to address a few issues you've mentioned in your comment:
To begin with, is it possible to consider the other states' lack of reaction to the U.S. attack as an endorsement of it or a change in the direction of the norms regulating the use of force? And I specifically refer, in this context, to the development of a new customary law exception to the prohibition on the use of force (notwithstanding the legal counterarguments brought about by Dapo Akande and, especially, the one regarding the jus cogens character of the prohibition on the use of force - I think that the states which reacted positively to the U.S. act used political language, not legal one, which, in my opinion, cannot amount to a change of the direction in the law of armed force.
Secondly, notwithstanding the prohibition of forced reprisals in international law, can the abovementioned acts be considered reprisals? On one hand, there is no consensus whether such action can be taken against violations of erga omnes obligations. The commentary to the ILC Articles On State Responsability states as regards countermeasures (but, for the sake of the argument, we'll consider that it applies to forced reprisals as well, ignoring the prohibition of such acts) that there is neither express prohibition - to such reactions when violations of erga omnes obligations occur -, nor express permission. However, I think that since such acts would preclude the wrongfulness of an otherwise international wrongful conduct, the interpretation given to the norms which permit such reaction must be restrictively interpreted. Thus, no express permission of such reaction (neither in the ILC Articles, nor within major international case-law which dealt with the issue, such as the The Gabčíkovo–Nagymaros Project or the Air Services Agreement between the U.S. and France, to my knowledge) leads me to believe that it is prohibited. On the other hand, you mentioned that "the clearly punitive statements of US agents seem to point towards reprisals". Again, even if we presumed that reprisals involving force were somehow justified, their function is to ensure compliance with international obligations of another state. If the U.S. acted with a punitive aim, can this be considered as an act of ensuring compliance by Syria with its international obligations? Perhaps only as an ancillary effect, but that was not the stated aim of the act, which cannot turn it into an act of reprisal.
I think that it would be very hard to justify even reprisals, when there are conflicting arguments which point to conclusions incompatible with the one that the U.S. act is an act of reaction aimed at ensuring compliance with international law.

Jordan Paust says

April 8, 2017

Article 2(4) expressly prohibits merely three types of force, not all uses of armed force. See writings of Reisman, McDougal, etc. Admittedly Article 51 does not apply re US self-defense, but it can be claimed that collective self-defense against the regime in west Syria and in connection with self-determination assistance to the Syrian people pertains. R2P supports this foem of collective self-defense and self-determination assistance. But so far the Trump administration speaks of punisment for international law violations.
Further, the textually attentive and policy-serving interpretation of Article 2(4) has room for self-determination assistance, human rights protection, security, and peace in the longterm. There is presently no disruprion of Syrian territory.

Jordan Paust says

April 8, 2017

R2P and Protective Intervention.

Olalekan Yussuf says

April 9, 2017

Thank you Monica.

Your conclusion clearly articulate a pragmatic approach. I equally agree with Veronica's supportive propositions on balancing compliance with the CWC/other legal obligations without diminishing the portent of 2/4 prohibitions.

I doubt the US would, howsoever, take such approach or make statement that may suggest or be interpreted as admission of violation of international norms on the use of force in this particular instance even if the action is strongly condemned by the international community (which is not the case at the moment).

It seems to me that any argument in support of the strike either premised on unsettled legal principles or practices (humanitarian intervention, R2P etc) or based on the reactions of majority of states, no matter how compelling or brilliantly made, will set grave precedent or further create uncertainty on legal principles on the prohibition of unilateral use of force.

Best regards

Jordan Paust says

April 9, 2017

Was another message (other than "punishment") one for China? -- look what I can do, and, yes, I am unpredictable, so you better take action re North Korea, and soon-- here comes our aircraft carrier.
Of course, that alone or coupled with "punishment," will not make the US act of war lawful.
Other questions: despite claims outlined in my R2P and Protective Intervention article, given the predictable widespread outcry of illegality under the Charter, what legal advice did the generals obtain from lawyers in DOD, the White House, the Department of State? If there was no effort to identify a claim that the act of war would be legal, why? Why especially because military officers must disobey clearly unlawful orders? Why especially because dozens of US Supreme Court decisions and opinions affirm that all members of the Executive Branch are bound by relevant treaties and customary international law?
Much for scholars to write about.

Matthias says

April 10, 2017

"Of course, the more states use forcible reprisals, the harder it is to treat them as one-off blips; the more they start looking like an uptick in states’ tolerance for unilateral force."

This seems to be the crux of the problem. Forcible reprisals are not in conformity with the ARSIWA, and enforcement of the CWC would either require the adoption of collective sanctions, or unilateral/multilateral peaceful countermeasures. The former are highly unlikely and, at this stage, the latter wouldn't exert much pressure on the Assad regime. We might regret this state of affairs, when faced with the horrid consequences of international paralysis in the face of Assad's many crimes. But should we, in our collective moral exhaustion, wish for greater flexibility of theses rules?

To construe this airstrike as an emerging exception to the general prohibition simply because we approve of the direction in which the violence is being exercised seems to set a very dangerous precedent.

Would we still be willing to support such arguments if, say, the Russian Federation were to officially bomb Ukrainian military positions on the grounds that they had allegedly used chemical weapons? Would anyone believe, then, that this operation was for the enforcement of the prohibition of chemical weapons?

Jordan Paust says

April 10, 2017

The 1993 assassination process, although interrupted, could also be viewed as an armed attack that had begun but that was blocked, like a North Korean missile that is fired from North Korea but blocked by a US missile. If so, self-defense might fit better than "reprisal," although it took some time to discover who ordered and began the process of attack.