The predominance today of "international criminal law" within public international law has meant a corresponding demotion of other areas of PIL - the law of international organizations, for example. But arguably the most important consequence of the fascination of the academic community with ICL (and with tribunals, the International Criminal Court, and all the apparatus that accompanies it) has been a somewhat dismaying lack of attention to the intellectual and legal space in which, from a practical standpoint, the most crucial activities of the laws of armed conflict actually take place. This is "operational" law of armed conflict - the planning of military operations to be in accordance with the laws of war, the formation of rules of engagement whether as a standing rules or specific rules for specific operations. Compliance with the laws of war doesn't happen by accident - it mostly happens because compliance with the rules is built into the operation from the very beginning, same as its logistics, strategic and tactical considerations, an essential part of the whole.
It is true that operational law of armed conflict is more limited as an activity around the world's militaries than one would like. Most militaries, let alone non-state insurgencies, rebel groups and guerrilla organizations, of course don't have military lawyers in quantity, if at all. To the extent that they engage in "operational" law, it is something embedded in general doctrines for operations, general considerations such as "don't target the civilians" or equally obvious legal principles, perhaps inherited in doctrine or the way in which operations are generally planned. Or perhaps from advice and training by the ICRC, or laws of war units of courses provided by the developed world's militaries through staff exchanges or sponsorships at the war colleges. Those are all important mechanisms of dissemination of knowledge and a sense of professional adherence to the laws of war among the world's military establishments. But the reality is that only a handful of states are able, and in fact do, invest heavily in military lawyers in the planning of operations, and the US most of all.
Still, in real life, operational law of armed conflict is a very big deal for the US military, at every level. It invests heavily in the JAG corps, in training and the application of the law in the planning and execution of operations. But for quite a long time, this investment was nearly invisible outside of the JAG. Academics were focused on the rising field of international criminal law; it seized (and largely remains seized of) the academic imagination. I have written elsewhere on why I think this over-attention is a mistake for public international law, but here I note that there has been some salutary pushback to create a better-rounded perspective, at least in the United States. To a considerable extent, this reflects the seeding of a handful of former senior JAG into the US legal academy in the last decade - they have gradually introduced a new academic speciality in operational law.
This new writing is genuinely academic in the sense that it is more than just operational manuals for JAG officers, limited in their audience to military practitioners. These practitioners-turned-academics are developing theoretical accounts of operational law issues. And although these writers do not always share the same views among themselves, there is a core orientation that at least partly defines "operational law" in an academic sense. Two of these core assumptions are:
(i) An assumption (not always shared by the international criminal law or human rights advocate viewpoints, and in any case not a general methodological assumption of those two perspectives) that those who are engaged in the planning of military operations are doing so in good faith; they are attempting to adapt provisions and principles of the laws of war to particular conditions, which are evolving and must be considered in a pragmatic sense, and that their efforts start from a safe harbor of good faith. So much so, in fact, that the issue of criminality (which tends to be the first question embraced by a sizable number of academic commentators in these areas) rarely arises; it has to involve some obviously extreme case that wouldn't arise in the planning of operations.
(ii) An assumption that the locus of operations and planning should be considered a party to a conflict - a "corporate" understanding of "who" is responsible for planning, execution, and adherence to the laws of war in the operation. Again, the focus is not on the (remote) possibility of individual liability, but instead on how a good faith operation ought to be conceived and carried out, where the responsibility is fundamentally "corporate" - i.e., attaches to a side.
As for readings in this area, they tend to start, unsurprisingly, with JAG and former JAG who have entered the legal academy. So, of course, former JAG such as Geoff Corn, Sean Watts, Eric Jensen, Mike Schmitt, Charlie Dunlap, Chris Jenks, James Schoettler, Victor Hansen (I'll stop before I get myself in trouble by leaving people off the list and with apologies to folks I didn't list here). Note that not all the former JAG write in exactly this vein of "operational law" - Mike Newton, for example, has largely focused in his writing on international criminal law and transnational justice issues. And there are others who have long military service records who now teach and write in these areas, but did not serve as JAG officers - Dave Glazier, for example, or Mike Lewis, and some who were JAG in militaries other than the US - Amos Guiora, for example - and some folks who are, well, sui generis (Tom Nachbar or the great Hays Parks).
Note too, that I'm deliberately leaving off an earlier generation of writers in these areas who precede the post-9/11 generation of JAG-turned-academics, Jordan Paust, for example. I also want to distinguish this from the related-but-different field of national security law - which, as folks like Bill Banks, John Norton Moore, or Bob Turner have set it out, is a broader academic category than the distinctly "operational" take on the international laws of armed conflict. There are also those who are those still in government such as Dick Jackson or, at West Point, John Dehn. And - an important part of what is likely to make this a lasting academic specialization - there are also some academics who, without a professional military background, have made this their speciality - Laurie Blank and the work of her clinic at Emory. Finally, let me mention two people who specialize in operational law issues outside the US - Ken Watkin and Ian Henderson. So, four readings as examples of the "operational law of armed conflict":
The Law of Armed Conflict: An Operational Approach. Geoffrey S. Corn, Victor Hansen, M. Christopher Jenks, Richard Jackson, Eric Talbot Jensen, James A. Schoettler, authors. (This is a new casebook to be released by Aspen in May 2012.)
The War on Terror and the Laws of War: A Military Perspective. Michael Lewis, Eric Jensen, Geoffrey Corn, Victor Hansen, Richard Jackson, James Schoettler, authors. (Oxford UP 2009).
Laurie R. Blank (I am listing her SSRN author page as the best way into her prolific writing on operational law issues, rather than any particular article - though I strongly recommend her most recent article, "Targeted Strikes: The Consequences of Blurring the Armed Conflict and Self-Defense Justifications.")
The US Practice of Collateral Damage Estimation and Mitigation. Gregory S. McNeal.
On the critical side, I should add that the operational law approach, while overall an enormously welcome addition to the academic approach to the law of war, does have certain blinders (at least as I would see it) with respect to the lawfulness concerning the use of force by actors other than the uniformed military - a certain discomfort, not to put to fine a point on it, to the use of force by civilian agents such as the CIA. That will be an important consideration in what seems to be the growing merger of CIA and JSOC special operations; the basis on which these different parties regard the lawfulness of other actors will matter.