Dan has two good posts addressing some of the legal criticism of the Israeli incursion into Gaza.
There's been a vigorous debate on the incursion across the wonderful new array of Foreign Policy blogs; David Rothkopf summarizes his dispute with Steven Walt here. Christian Brose has a compelling piece here, too. While the writers don't focus on international law, they discuss whether Israel had adequate justification for the incursion, which certainly has jus ad bellum overtones. (To my mind, Brose has the best of the historical debate, but except to vehement partisans of one side or the other, I don't think it has much relevance; I seriously doubt decades-old events have any weight in determining whether, morally or legally, a country is justified in responding with force when force is used against it and here, there's no question force was used against Israel – thousands of rockets hit Israeli cities every year, and no country has an obligation under international law to live under constant bombardment).
Unsurprisingly, Michael Walzer – probably the greatest living just war theorist – has provided the best analysis I’ve seen of the actual jus in bello question, which is, how does the conflict square with international law's proportionality requirements. I want to make two critical points about proportionality, based on but hopefully not merely duplicative of Walzer's work:
(1) Proportionality has to do not with the harms each side has inflicted on the other – neither international law nor the traditional ethics of armed conflict require every war to end in a tie – but with proportionality of means to ends. Put otherwise, targeting civilians is impermissible, but some civilian casualties are inevitable in any armed conflict, so to say any civilian casualty violates the law of war would render meaningless the UN Charter's grant to every country of the right to use force in self-defense. Rather, the force a country uses should not be excessive in light of the military ends it seeks to achieve. The legitimacy of those ends is a separate question.
(2) That sort of means-ends reasoning is difficult to do and tends, in practice, to involve the reasoner's – rather than the acting country's – judgment as to the importance of military ends. It's also sometimes hard to achieve on the basis of open-source intelligence.
Moreover, a strategic error in the military context is not automatically a war crime; if it turns out that a military action doesn't achieve the end in question, that doesn't make it disproportionate, just foolish.
That said, focusing on the jus in bello questions about the incursion, there are probably two other critical issues: (1) what have the military and civilian consequences of the Israeli action been, and (2) what steps has the IDF taken to minimize civilian consequences.
The first is very difficult to answer. Early on in the conflict, CNN was reporting 400 fatalities, 350 militant and 50 civilian, based on Palestinian medical sources. Dan points to more recent numbers in excess of 700 casualties, with more than 300 civilian; it's unlikely both sets of numbers are right, and incredibly difficult to tell which to believe. The first number, of course, represents incredibly accurate targeting for urban warfare, which suggests Israel's been diligent about minimizing civilian casualties and that the military consequences outweigh the civilian ones. The second represents less accurate targeting, which raises less of an inference of diligence.
As to the second question, we do have some information about what steps Israel's taken. Ha’aretz – an Israeli paper often critical of the IDF – reports:
The IDF has made frequent use of what is known as “knocking on the roof”: Militants are warned by phone when a residential building used to store arms will be bombed, and told to vacate the premised together with their neighbors. The weapons caches are hit only after the residents leave.
Hamas has tried placing civilians on the roofs of such buildings when the phone call warning comes in. In these cases, the IDF fired antitank missiles near the building, and in a few cases the residents left.
Letting your enemy know what targets you’re going to strike before you do it is a major concession with no strategic benefit – and seems to exceed the typical attempts by conventional forces to protect enemy civilians. Given Israel's efforts to prevent civilian casualties and reported success focusing attacks on militants even in a difficult urban environment, it appears for now that traditional jus in bello norms have probably been satisfied (in general; evaluating whether particular targeting decisions were based on reasonable belief that they were directed at legitimate military targets using proportional force is probably impossible during a conflict).
Generally, the fact that the article (and plenty of other open-source reporting) reveals Hamas is effectively hiding behind its own civilians makes the application of these criteria even more difficult than usual. Traditional just war theory presumed that of course a country wanted to protect its own civilians to the extent it was possible, and demanded that belligerent parties take steps to protect civilians including putting distinguishing marks, like uniforms, on military personnel. Imposing obligations to protect those enemy civilians who the enemy has purposefully endangered wouldn't have occurred to the drafters of the Hague Convention on Armed Conflict a century ago.
None of this is to say civilian casualties aren't tragic or upsetting, and of course we all hope for a swift and just end to any military conflict and recognize and mourn its human costs. It's merely to say tragedies are an inevitable part of war, but some wars are lawful, and tactical decisions during a war are judged not by whether they are tragic, but whether they adhere to particular established rules.
