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Wednesday, September 04, 2013

The Legal Case for Intervening in Syria (Anthony Colangelo Guesting)

An International Legal Case for Military Intervention in Syria  

By Anthony J. Colangelo

Does international law allow U.S. military intervention in Syria? The Obama Administration has advanced a number of possible justifications including self-defense, halting civilian deaths, and debilitating the Assad regime’s chemical weapons capabilities. None of these justify intervention on the current state of international law.

Yet that doesn’t mean international law would view a U.S. intervention as illegal in the long run. International law is a tricky sort of law, and the United States could make a strong legal argument that intervention would help change the law to allow interventions to halt mass human rights abuses. Going forward, this argument could retrospectively ratify U.S. intervention in Syria and give the United States a central role in formulating international legal criteria for future interventions.  

Legal arguments against intervention are straightforward and rely principally on treaty law. Most prominently, the U.N. Charter prohibits the “use of force against the territorial integrity or political independence of any state.” There are only two ways intervention is permissible under the Charter: the Security Council authorizes it, which has not and will not happen, or the United States acts in self-defense. Even the very best international lawyers can’t stretch the doctrine of self-defense to cover a U.S. strike in these circumstances. Even if they could, that’s both an awful and an awfully expansive precedent.

The Administration has also seized upon the Assad regime’s evident use of chemical weapons as a violation of international law that justifies intervention. Yet here too, treaty law cuts the other way. Syria is not a party to recent treaties banning the use of such weapons. Because treaties bind only states that have agreed to be bound by them, Syria’s use of chemical weapons cannot violate the treaties. The only treaty banning the use of chemical weapons Syria is a party to addresses international, not internal, conflicts. And in any event, it doesn’t authorize states to attack other states that violate it. In sum, treaty law does not allow intervention in Syria.

There is, however, another type of international law that might allow intervention, called customary international law. Unlike treaty law, customary international law doesn’t derive from formal agreements among states. Instead, it arises from the practice of states accompanied by what international lawyers call opinio juris, or states’ intent that their practice carries legal significance.

States can usually treaty around custom much the same way private individuals can contract around the norms that govern our everyday behavior. But there are some rules of customary international law that cannot be contracted around and that override treaties inconsistent with their rules. These are called jus cogens, or peremptory norms of international law. Jus cogens contain prohibitions on serious international law violations like genocide, torture, slavery, and crimes against humanity. To illustrate, Hitler and Mussolini can agree by treaty to afford each other’s nations certain preferential trade treatment. But they cannot enter into a treaty legalizing genocide. Jus cogens would swoop in to invalidate that treaty as contrary to a peremptory norm of international law.               

Where does this leave the international legal justification for intervention in Syria? Many favoring intervention have cited jus cogens prohibitions on mass human rights abuses as justification. But that argument is flawed because the jus cogens norm does not directly conflict with the U.N. Charter’s prohibition on the use of force. That is, the Charter doesn’t authorize human rights abuses—in fact, just the opposite: it seeks to “promot[e] and encourage[e] respect for human rights.” Thus even if one can safely classify the Assad regime’s abuses as violations of jus cogens, that only gets the argument halfway to intervention. To justify intervention, the jus cogens norm would need to encompass not only a prohibition on human rights abuses but also the capacity of other states to enforce that prohibition. This latter enforcement component is presently lacking under the law. Finally, the Charter’s prohibition on the use of force isn’t some run-of-the-mill international rule. It is a cornerstone of the postwar international legal system that outlaws aggressive war. For this reason, the prohibition on the use of force is itself considered a jus cogens norm.        

Nonetheless, it may be time for a change. Because customary international law arises from state practice, as practices change so too does the law, including the law of jus cogens. One way customary international law changes is states break it to form new norms; breaches effectively plant the seeds from which new norms grow. Although a breach may violate international law when it occurs, the law may develop to ratify that breach as the early stage of a new norm’s development.  

If the United States intervenes in Syria, it has an initial international legal choice to make: it can ignore international law or seek to justify intervention within it. The second option’s benefit is that if state practice develops to allow intervention the illegality of U.S. action will wilt as the new norm blossoms. Yet some may view this option as undesirable precisely because it may prompt other states to accept the legality of intervention. Reciprocity is also a cardinal rule of international law: if it’s legal for us, it’s legal for you.

The question then becomes whether it’s better to operate within the law or outside it. For other states also will face that same initial choice above, to which this first-order reciprocity norm also extends; that is, the initial choice to ignore law or to justify their actions within it. In this respect, the United States may actually derive two distinct benefits from choosing to justify its actions under international law: a retrospective ratification of U.S. intervention and the ability to formulate criteria for a budding international law of humanitarian intervention.   


Posted by Dan Markel on September 4, 2013 at 01:44 PM in Article Spotlight, Current Affairs, International Law | Permalink


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Isn't there a difference between a bilateral treaty violating what might be considered jus cogens, and virtually every country in the world ratifying such a treaty? Isn't the later the kind of thing that is evidence that a particular norm is universal to begin with? And if the law against aggression is itself jus cogen, is there any precedent at all for reversing such a norm?

This seems like a real stretch to me. The form of argument would allow you to justify anything. Either you are following international law or you are breaking international law in the hopes of changing it.

Posted by: brad | Sep 4, 2013 5:34:21 PM

Thank you for your questions and comments.

International law contemplates the modification of jus cogens. Here it would be modification of the norm against the use of force so as to give way, in limited circumstances, when that norm shields regimes perpetrating mass atrocities—the prohibition of which is also jus cogens. We’re not talking about a wholesale acceptance of the legality of aggressive war. This is precisely why, in my view, the United States should seek to justify its actions with international legal argument should we decide to intervene. That argument will have a constraining effect on any future interventions. On the other hand, if the United States simply ignores international law then it’s a free-for-all; other states also may feel free to ignore international law. We have a vested interest in the maintenance of international law generally even if we choose to break it in a specific situation. Which leads to the second point: it’s not true that you are either following international law or you are breaking it in the hopes of changing it. You could be breaking it, period. The key element is the expression of opinio juris, which would be the United States seeking to justify the intervention under international law. It is true that this argument would allow you to justify anything—provided other states agree going forward. But that’s how customary international law changes. It’s not a stretch; it’s just how this particular form of law works.

Posted by: Anthony Colangelo | Sep 4, 2013 6:24:23 PM

I have always been somewhat mystified by the workings of international law. This explanation of how it applies in the specific context of Syria is extremely helpful.

Posted by: Susannah Pollvogt | Sep 5, 2013 8:26:07 AM


I share Brad's skepticism, and would like you to elaborate on something. You write that by supplying a justification under International Law, the U.S. would not actually be breaking International Law, notwithstanding the fact that action being justified would not heretofore have been widely recognized as lawful. No problem, you say - either the U.S. will fail to persuade other countries (in which case, I presume, we will retrospectively view the now-historical U.S. action as unlawful - or the U.S. will be successful, in which case the "new" International Law will merely confirm that the U.S. had it right all along.

This is interesting (at least to skeptics) in several ways, but I'd like to focus on one: At what point will we know that the U.S. argument has been rejected? Would acquiescence by lots of the "right" countries, and scholars learned in international law (who I believe are a legitimizing source for customary IL) be enough? What if several countries agreed with the U.S., but failed to get a treaty ratified by a majority of countries?

Note also that this process, which the rest of the world hardly seems inclined to expedite in the case of Syria, could take some time. What would the lawfulness of the historic U.S. action be during this extended period of suspense?

Finally, how can the processes you describe realistically achieve conclusivity? I see nothing to prevent successive U.S. presidents from asserting a position that the rest of the world does not really subscribe to, but also declines to oppose formally. Would it really be your position that a U.S. president in 2040 (George P. Bush, perhaps?) would be entitled to make the same case for invading a reinvigorated Iraq that you urge Obama to make with regard to Syria? Namely: "I know this STILL isn't recognized as legal, but Obama was right a quarter-century ago, and this position is still correct now. My administration is determined to keep making the case until the rest of the world agrees." What principle of actual...law would prevent George P. from doing this?

Adam Scales

Posted by: Adam Scales | Sep 5, 2013 11:56:19 AM

Slight correction: as hastily written, my fourth paragraph partially replicates the second. To simplify, I'm asking about conclusivity going either way - how much is (just) enough to know when the position has become "law", and at what point should IL "give up" on the proposed justification so becoming? Sorry for any confusion.


Posted by: Adam Scales | Sep 5, 2013 12:04:45 PM

Adam, these are great questions and I hope you will forgive me if I’m unable to provide definitive answers to all of them—say, the exact number of states necessary to form customary international law, something I don’t think anybody knows for certain.

Let me start by clarifying that I’m not arguing that by seeking to justify intervention under international law “the U.S. would not actually be breaking international law.” Rather, my argument is that nothing being advanced right now, including stopping mass human rights abuses, can “justify intervention on the current state of international law. Yet that doesn’t mean international law would view a U.S. intervention as illegal in the long run.” This is because: “Although a breach may violate international law when it occurs, the law may develop to ratify that breach as the early stage of a new norm’s development.” Accordingly, “if state practice develops to allow intervention the illegality of U.S. action will wilt as the new norm blossoms.” So there would be a breach; the real question I’m trying to address is how international law views that breach going forward.

Which brings us to your conclusiveness question. But before I try to answer that I would like to reemphasize thrust of my argument: if the United States simply ignores international law, there is a breach, period. That state practice will not “count,” so to speak, toward the development of a new norm. It also weakens the rule of international law generally. Seeking to justify intervention with international legal argument, however, bestows opinio juris and tends to uphold the rule of international law generally even while trying to modify one of its norms.

So how can we tell when the norm has changed? It is true that other states may not view humanitarian intervention as permissible going forward, and thus even if the United States intransigently insists upon its legality the United States is just wrong and the breach endures. But other states may come around to viewing a limited humanitarian intervention as acceptable. As you allude to, one easy way to achieve conclusiveness is a treaty essentially codifying the customary norm. For example, after World War II the Genocide Convention “confirm[ed] that genocide . . . is a crime under international law.” But there may not always be a treaty. And a treaty is not always necessary. For a long time, the vast majority of international law was customary. The basic methodology is that some major proportion of the world’s nations agree the practice is legal. This agreement can take any number of forms including, as you say, acquiescence, particularly on the part of states not directly involved in the dispute. And a norm may well be in legal limbo while this practice either accumulates or fails to accumulate. In this regard, international law is a fundamentally empirical phenomenon. I would also hasten to add that international law scholars are not themselves a legitimizing a source of customary international law. Their views merely assist the empirical assessment of the law to the extent they describe what state practice is, not what it should be.

I hope I’ve been able to answer some of your great questions.


Posted by: Anthony Colangelo | Sep 5, 2013 1:47:56 PM


Is your analysis offered in anticipation of a broader "military intervention" in Syria than the "punitive" strikes that are presently being discussed? I ask because your analysis seems to assume a humanitarian intervention--i.e., one calculated to halt civilian attrocities--which is at odds with the nature of the strikes for which authorization has been sought.

The processes by which CIL evolves is an interesting angle; I too have given some thought to this in relation to the Syria situation, and concluded that it would not render the contemplated strikes lawful.

It is true, as you observe, that rules of customary international law can (and are) overtaken by contrary practice. But this process of law formation (and adjustment) is much better suited to, say, rules governing the ways in which States delineate maritime zones or the outer limits of their continental shelf than modifying a jus cogens norm. As you observe, the non-intervention rule embodied in 2(4) was recognized as a jus cogens in the Nicaragua case (I recall both the U.S. and Nicaragua were in accord on this point). If you accept Art. 53 VCLT as authoritative on jus cogens, a jus cogens norm can be modified only by a subsequent norm of general international law having the same character. I personally think it is a stretch that practice--and the legal justifications offered for that practice--surrounding the Syria case could give rise to a rule of CIL. I cannot contemplate how this practice and accompanying justifications could be said to give rise to a peremptory norm "accepted and recognized by the international community as a whole as a norm for which no derogation is permitted."

The Nicaragua judgment is relevant for another point. The ICJ took jurisdiction in that case having found that the CIL non-intervention rule was not displaced by the conventional rule in the Charter. Your analysis addresses how subsequent practice may modify the CIL rule, but do you contend that it would also overtake the conventional rule in the UN Charter? That would be a startling development in light of Article 103 of the Charter.

Finally, I understand your overall point to be that if the USG strikes Syria, it should not be silent on international law, but should carefully articulate a legal justification with an eye toward the future. I couldn't agree more. My own view is that this justification will not attempt to lay the groundwork for a "humanitarian intervention" norm. In the wake of the 1999 NATO air campaign over Belgrade, the Acting Legal Adviser at the State Department went to some lengths, in articulating a particularized legal basis for the strikes, to make clear that the USG/allies had not accepted a doctrine of humanitarian intervention as an independent legal justification.

Thank you for taking the time to share your ideas.

Posted by: Brian | Sep 5, 2013 2:27:09 PM

Brian, thank you for these very informed and insightful questions and comments. I am indeed arguing for a humanitarian intervention justification. Which is not to say that the administration has taken or will take that position in its words or deeds.

I can certainly appreciate your difficulty contemplating a jus cogens norm permitting intervention. These norms tend to be cast as prohibitions rather than authorizations: No genocide. No torture. No aggressive war. What I have in mind is an enlargement of the existing jus cogens norm against atrocities to encompass some enforcement mechanism where the U.N. fails to uphold its own commitments to human rights. If these are in fact norms from which “no derogation is permitted,” international law should not permit derogations. And if the norm enlarges to authorize enforcement, it would trump a treaty—the Charter—to the contrary.


Posted by: Anthony Colangelo | Sep 5, 2013 7:02:27 PM

Another question if you don't mind.

If opinio juris are actions by states under the understanding that they are legally required, is it in some sense too late? Wouldn't any white paper at this point be, and be seen, as post hoc justitification rather than an explanation of motives? Or does that sort of subjectivity not matter much in int'l law?

Thanks for an interesting post and clarifying responses.

Posted by: Brad | Sep 5, 2013 7:46:31 PM

Brad, another interesting question. Opinio juris would take the form of explaining why the action is justified under international law. If I’m reading your question right, you are asking about when that justification must be articulated. The strongest evidence of opinio juris would probably be before and during the action, though I don’t imagine a post hoc justification would carry no weight at all for a customary international law analysis. It also may be that more than one justification is advanced. In this respect, there can be a sort of throwing spaghetti, and maybe some capellini and linguine too, at the wall quality to the process.

Posted by: Anthony Colangelo | Sep 6, 2013 9:34:17 AM

Brad, sorry – I had this lingering feeling I wasn’t understanding your question so I looked up “post hoc justification” (or “rationalization,” which popped up a lot). I was relying on my high-school Latin to answer your question the first time. I think the answer to your question is no, international law does not care about that type of subjectivity, at least the first time. But it definitely does care if states rely on that justification to justify their own actions in the future. That’s how it’s made. It's also why I am urging the argument I am.

Posted by: Anthony Colangelo | Sep 9, 2013 9:50:03 PM

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