Editor’s Note: Just Security is holding a “mini forum” on the new Defense Department Law of War Manual. This series includes posts from Sean Watts, Eric Jensen, Adil Ahmad Haque, Geoffrey Corn, Charlie Dunlap, Jr., and more to come.

Similar to my good friend Eric Jensen, the first thing that came to mind regarding the new Defense Department Law of War Manual is its limited stated purpose. I want to consider the manual’s limited purpose against its broader potential to make a significant contribution to the customary international law of war. Perhaps this is because I am currently teaching in Rome and encouraging my students to think critically about the theory and evidences of customary international law. This post will briefly consider the manual’s unfortunate attempt to limit its impact upon international and domestic law and instead suggest that it should be afforded significant weight well beyond the DOD.

First, high praise is due to the DOD for publishing the manual and thereby helping to clarify that international laws of war are, in fact, laws applicable to the United States and its military. While it may seem odd to mention this, it is an unfortunate necessity given the extreme reluctance of some federal courts and judges to treat international law generally and the law of war specifically as … well … law. As DOD General Counsel Preston said in his foreword, however, the law of war “is of fundamental importance to the Armed Forces” and “is part of who we are.” He further stated, “[u]nderstanding our duties imposed by the law of war and our rights under it is essential to our service in the nation’s defense.” While the manual later seems to hedge on this notion by stating that it “is not intended to, and does not, create any right or benefit, substantive or procedural, enforceable at law or in equity against the United States, its departments, agencies, or other entities, its officers or employees, or any other person,” this passage states but a truism. The manual does not create rights or benefits. The international law that it purports to articulate does. And until relatively recently federal courts have traditionally recognized and upheld these rights and obligations in cases properly submitted to them.

Regarding the manual’s potential impact on the substance of international law, it is beyond dispute that official government publications like the manual are strong evidence of state practice and opinio juris, thereby supporting the existence and clarifying the content of customary international law. Though former State Department Legal Advisor John Bellinger and former DOD General Counsel Haynes criticized the International Committee of the Red Cross law of war study’s heavy reliance on military manuals rather than “actual” state practice in armed conflict, such arguments seem weak at best and are potentially specious at worst.

A fair argument can be made that what states say about the law of war is more important than what they do in the throes and uncertainty of armed conflict. First, when stating law rather than policy, a military manual is perhaps the clearest expression of opinio juris. Actual state practice in armed conflict is often unaccompanied by expressions of opinio juris. More importantly, during armed conflict, the law of war’s fundamental values are challenged by utilitarian moral reasoning. Need proof? Consider the fact that the manual repeatedly emphasizes an absolute requirement for the humane treatment of all individuals detained in any type of armed conflict as well as an absolute prohibition of torture. Which should be considered stronger evidence of customary international law: actual US practice during the G.W. Bush administration (justified by the mantra of “saving American lives”) or this manual? That the answer is the manual seems rather self-evident.

If understood to contain clearer and more accurate statements of law, then the manual could significantly influence the content and perceived strength of customary international law of war norms both within and beyond the United States. This might particularly be the case because the US government views itself as a “specially affected state” whose practice is more meaningful in the development of customary international laws of war than those of states that rarely engage in armed conflict. (See para. 1.8.2 and related notes for more on this point.)

Unfortunately, the manual undermines (Eric might say intentionally) its potential importance with a disclaimer:

This manual represents the legal views of the Department of Defense. … Although the preparation of this manual has benefited from the participation of lawyers from the Department of State and the Department of Justice, this manual does not necessarily reflect the views of any other department or agency of the U.S. Government or the views of the U.S. Government as a whole.

This statement is as frustrating as it seems foolish. Why would the views of the DOD — the only true war-fighting arm of the US government — regarding the law of war “not necessarily” reflect the actual views of the entire US government? The answer is undoubtedly that without this disclaimer other agencies of the federal government would have strongly objected to the manual’s publication. We should therefore not allow this disclaimer to detract from the effect of the Manual as an expression of opinio juris.

Indeed, one might say that the DOD is the foremost specially affected agency of the US government than most other federal agencies. Given the DOD’s long history of and experience with discerning, articulating, and applying the law of war, those other agencies and the federal courts would do well to carefully consider and afford great weight to the manual. Its statements regarding the international law of war are likely to be more precise and more cogent.

This is not to say that the manual is perfect, which has in one respect already been shown here. In such cases we must recall the manual’s other precaution,

This manual is not a substitute for the careful practice of law. As specific legal issues arise, legal advisers should consider relevant legal and policy materials (e.g., treaty provisions, judicial decisions, past U.S. practice, regulations, and doctrine), and should apply the law to the specific factual circumstances.

With this caveat, the manual is an important, positive step in the United States’ relationship with international laws of war. It should rightly have salient effects well beyond the Armed Forces.