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

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.