A few days ago, French President Macron reportedly said that the use of chemical weapons in Syria would cross a “red line” for France and result in reprisals. Macron’s statement comes less than two months after the United States conducted airstrikes against Syria for its use of chemical weapons. The vast majority of states that spoke about the U.S. operation supported or were non-committal about it. Very few states condemned it as unlawful. By contrast, most commentators contended that the operation was unlawful. (See the blog posts collected here.) The operation was inconsistent with the longstanding interpretation of Article 2(4) of the UN Charter and not covered by either of the Charter exceptions. Moreover, though there is an ongoing debate about whether the jus ad bellum contains a third exception for humanitarian interventions, the majority view is that it does not. The reason for this view is that, even when states (as a group) appear to condone particular operations that might be characterized as unilateral humanitarian interventions, states decline to articulate the opinio juris that is necessary to establish a new, generally applicable exception to Article 2(4). And in any event, the U.S. operation in April seemed more like a reprisal than like a humanitarian intervention.
So, what should we make of Macron’s statement? When news of it broke, I tweeted this comment:
Several people objected to my tweet. I am continuing the conversation here because I thought it might be of interest to a broader audience, and because its implications go far beyond Macron’s statement. It has to do with how we understand and assess the jus ad bellum.
The principal objection to my tweet was that there is not sufficient opinio juris for a change in the law. Again, most states have not demonstrated that they support a new exception to Article 2(4) or that they want to expand considerably an existing exception. Some scholars have questioned whether that kind of opinio juris is really necessary for humanitarian interventions to be lawful. But I don’t want to go down that road here.
In my view, it’s clear that, in April, states were trying to balance two competing considerations. They supported the operation against Syria to deter the use of chemical weapons, but they did not want to expand the exceptions to Article 2(4). They were trying to assess the U.S. operation based on its particular facts—to treat it as a one-off incident, rather than evidence of a new, generally applicable substantive standard. So, let’s assume for now, that states did not create or endorse a new norm permitting unilateral humanitarian interventions or reprisals.
It would not follow that the law weathered the April incident without change. Any international incident that puts a legal norm at issue communicates not just whether the norm is “good law” but also the extent to which global actors are willing to stand by it and prioritize it against other norms. Of course, legal norms routinely conflict with one another and push in different directions. Because Article 2(4) has unique standing in the legal order, it almost always prevails in these situations. But in the Syria case, Article 2(4) was in tension with another very important legal norm—the ban on chemical weapons. This ban means little if it is repeatedly violated with impunity. And although it usually is upheld without budging on Article 2(4), that option wasn’t working in Syria. In the event, most states that addressed the issue decided that Article 2(4) ought to bend for the ban on chemical weapons. Macron’s recent statement indicates that France would make the same decision again.
For me, this pattern of behavior demonstrates that expectations on the relationship between Article 2(4) and the ban on chemical weapons have shifted—not necessarily for all cases but in the context of the Syria conflict. For those who are interested in preserving the jus ad bellum’s regulatory force, the follow-up question is how best to limit the precedential effect of the Syria strikes, such that they do not invite less palatable deviations from Article 2(4) in the future. That question has come up before, but it does not have easy answers. I offered my initial views on it here. Anthea Roberts disagreed with me, and I then commented on her post here.
Although the question is difficult, two answers that are commonly proffered strike me as either nonresponsive or not credible. First, it is insufficient simply to insist that the April strikes were unlawful and had no effect on the law. Even if we assume that states did not create a new exception to Article 2(4), we have to accept that states, as a group, declined to apply the Article 2(4) prohibition in Syria. They decided to deprive the prohibition both of its operational relevance and of its normative bite. That looks an awful lot like a decision to make the strikes lawful. Or at least, it means that the difference between calling them lawful and calling them unlawful is, as a practical matter, imperceptible. Legal analysts ought to grapple with that reality.
Second and for the same reason, commentators cannot plausibly “hold the line” on the jus ad bellum by pretending that it is somewhere other than where states themselves have taken it. For good or for ill, states reacted to the April strikes as they did. The task now is to assess, and perhaps to try to shape, how their reaction will affect the jus ad bellum going forward.