Geoffry Corn comments on proportionality in jus in bello

(Welcome instapundit readers! The original instapundit link which was bad (my fault) is here, on proportionality jus ad bellum.)

Geoffry Corn, former chief of the Army JAG Corps Law of War Branch and now a professor at South Texas College of Law and, perhaps most importantly, an alum guest blogger at Opinio Juris, was kind enough to send a comment on my earlier blog post on proportionality. It is characteristically thoughtful and expert and sufficiently important to put up as a separate post:

This is Geoff Corn from South Texas. As a retired JAG Officer and former Chief of the Army JAG Corps Law of War Branch I wanted to let you know that I thought your post in response to some of the commentary on the "rule of proportionality" was both timely and essential. I could not agree more with you regarding your comments related to mixing up the ad bellum and in bello concepts.

What really strikes me as surprising is the general failure to cite the precise language of AP I. I can tell you from experience that Judge Advocates here and in other militaries are taught to focus on that language, and the use of the term "excessive." No where to my knowledge does Article 51, which most would regard as the most comprehensive effort to "codify" the principle, use the term "disproportionate."

Military commanders are advised that this is not an insignificant word choice. The term excessive seems to suggest a different balance in the jus in bello than that applied to the jus ad bellum.

I am also surprised that the link between this principle and the express prohibition against indiscriminate attacks has not been better explained in some of these commentaries. JAGs are taught a fairly straight forward equation: Indiscriminate attacks are illegal. The fall into two categories: intentionally indiscriminate (targeting a non-military objective or employing a method or means that cannot be controlled), and "implicitly" indiscriminate: targeting a lawful military objective with the expectation that the collateral damage or incidental injury will be excessive in relation to the concrete and direct military advantage anticipated.

You are dead on target (no pun) with regard to your comments about differing interpretations of these terms. I have personally studied with IDF lawyers, and I have no doubt they know the law, and are advising compliance. It is these differing perspectives that will no doubt be exposed as underlying the decisions being made.