What is The Common Law of War?  

Since the recent al Bahlul en banc decision before the D.C. Circuit, I have been thinking a lot about the Common Law of War. As others have already analyzed in detail (Steve, Peter, Jonathan, Marty & Steve), the D.C. Circuit upheld Bahlul’s conviction for conspiracy but threw out his conviction for material support for terrorism and solicitation. Material support and solicitation are unavailable for pre-2006 conduct because they are neither international crimes nor historically charged before military commissions. Conspiracy, on the other hand, is a different story. While it seems pretty clear that conspiracy is not a stand-alone offense under international law, the government has relied on the argument that conspiracy is historically chargeable before a military commission as part of the “common law of war.”

The exact status of the common law of war theory remains unknown because the court’s majority applied “plain error” review and not de novo review on the merits. Some judges concluded that Bahlul waived his objections by not raising them at trial (when Bahlul was declining legal assistance). For his part, Judge Kavanaugh appeared sympathetic to the common law of war argument, which arguably departs from his previous notes of skepticism regarding the theory in Hamdan II.

Since the common law of war idea is still wide open, I’ve been trying to come to terms with it and articulate precisely why I’ve been uncomfortable with it in the past. Indeed, when I first heard the government’s assertion of this theory, I was deeply skeptical and found it almost outrageous. The law of war is international by definition—it is the same for everyone and that’s the whole point of it. The law of war is based on reciprocity and it makes no sense to think of it as a creature of domestic law.

That being said, I think the issue is more complicated than I initially assumed.  In particular, it is important to note that Lieber himself makes reference to the common law of war in article 13 of the Lieber Code. Also, Richard Baxter, in his famous article on spies and unprivileged belligerency, concludes that acts of belligerency by an unprivileged belligerent simply aren’t violations of international law at all – they are violations of domestic criminal law. That’s absolutely correct. The absence of the privilege means that the unprivileged belligerent cannot exempt himself from the demands of domestic law. That’s something far different from an international crime. Unfortunately, Baxter also says in the preceding sentence that the saboteurs in Ex Parte Quirin were “no doubt” triable under the statutes and “military common law of the captors” – though he never explains what he means by this. Presumably he felt that the saboteurs in Quirin were subject to military commission jurisdiction despite the fact that their crimes were domestic violations, though he never articulates his reasoning. Of course, I don’t want to parse Baxter’s article like it’s gospel; I find there’s too much of that already with people treating semi-authoritative Commentaries like treaties. But I still find it interesting that both Baxter and Lieber used the phrase or something close to it.

So why is it so difficult to understand the common law of war? Here are four possible reasons:

1. We no longer live a common law world. Well not exactly. The U.S. is still part of the common law, in the historical sense, but really the common law doesn’t play the role it once did. It has substantially evolved. Statutes and regulations play a much larger role now – and this applies in almost every field of law. This certainly applies in the criminal law, where even the idea of a common law crime sounds just bizarre to today’s students. It’s just so far removed from how the law operates today.

2. Although state courts in the U.S. continue to evolve the common law in each jurisdiction in subject areas that are not covered by a particular statute (say tort law), this endeavor is temporally removed from its historical roots in common law England. Although the law in each jurisdiction can all be traced back to a common source, the doctrines have been developed in unique and different ways in each court. The common law – as something truly common across jurisdictions – has receded into history.

3. The law of war in general, and the jurisdiction of military commissions in particular, were woefully under-theorized in previous generations. This was certainly true in the Civil War, when other than Ex Parte Milligan as an enduring constraint on military jurisdiction, there was insufficient attention paid to developing a deep theory of military jurisdiction. Famously, Ex Parte Quirin was a rush decision, arguably fast-tracked because the Supreme Court was concerned that the administration might execute the prisoners before a decision was reached – which would have dealt a near-fatal blow to the Supreme Court’s institutional legitimacy and its self-asserted purview, announced in Madison v. Marbury, to say what the law is. It is no surprise that we now look back on Quirin as “not this Court’s finest hour” (Hamdi v. Rumsfeld, Scalia J. dissenting). One way of putting the point is to follow Steve Vladeck and say that the Court has never fully rationalized why military commissions are exempt from the Article III requirement of trial before a regular court. Another way of putting the point is that during the Civil War the concept of military jurisdiction was under-theorized and we are only now playing catch-up.

4. There is something that unites our use of the terms “international law” today with how the term “common law” might have been used in previous generations. This might help explain why there is an international law of war today and a common law of war in the past.  Although they are different, what unites them is a shared participation in a larger legal culture. For international law, the larger legal culture is the international order, with its unique sources for lawmaking (treaties, custom, etc.) and international organizations. For the common law, the larger legal culture is the law that is “common” to many jurisdictions who are all participating in a common legal culture and apply its law together – the “common law.” Although the common law is not the same as international law, it is something larger than pure domestic law, and as such it could, in theory, and historically as well, fulfill some of the demands of reciprocity that the laws of war demand. The problem, of course, is that the common law doesn’t function that way in today’s world. The whole point of the law of war is that it has to be bigger than just domestic law. And maybe the common law in the past was just big enough to support the law of war in some limited sense. Whether that’s enough in today’s world, I really don’t know.