Most people that throw around the accusation of “disproportionate response” refer to some vague conception of approximate parity in casualties and means. In fact, as I noted yesterday, international law has its own definition of “disproportionality”, which is both quite specific and rather different from the use in common parlance. (Just like “insanity” for legal purposes is not some vague term for crazy behavior but a term of art with a precise definition.)
Humanitarian law expert Prof. Laurie Blank, on the Volokh Conspiracy group-blog, gives a long expose on the meaning of “disproportionality”, following her earlier op-ed elsewhere. (H/t: commenter “VultureTX” at an Elder of Ziyon piece on proportionality in the Gaza War.)
[…] proportionality is more than just a principle; it is a methodology for assessing lawfulness in advance through careful consideration of both the value of the military advantage and the likelihood of civilian casualties. The principle tells us what we are trying to achieve — a balance between military needs and humanitarian concerns that minimizes civilian harm as much as possible. […] As I note in my earlier piece, “Asymmetries and Proportionalities,” assessing the legality of an attack that results in civilian casualties must be done prospectively, based on the information the commander knew or should have known at the time of the attack. The standard is “reasonableness” — whether a reasonable commander in the same position would determine, based on the information available at the time, that the expected civilian casualties would be excessive in light of the anticipated military advantage.
Key to this assessment is not whether the court, the media, or anyone else thinks the decision was right or would have actually made the very same decision. Nor is it whether any resulting casualties seemed or even were excessive afterwards. The controlling factor in assessing proportionality after an attack is whether the commander’s determination—that the likely civilian casualties in that operation would not be excessive—was reasonable. This reasonableness assessment can only be made with a full understanding of the situation and all relevant information at the time of the attack — and, just as important — an awareness of what is considered to be reasonable in light of general practice.
International tribunals have rarely undertaken this analysis. This may well be simply because they have no lack of much easier and obvious cases. Their dockets can easily be filled to overflowing with the staggering number of deliberate crimes against civilians […] The difficulty in translating the proportionality rule from the operational dynamic of the battlefield and the fog of war to the evidence-bound confines of the courtroom is certainly another factor. The few instances of adjudication, however, consistently reinforce both the prospective approach and reasonableness as the touchstones of the analysis. Responsible militaries, for their part, investigate and review every incident involving civilian casualties to determine whether further investigation or prosecution is warranted—and simply to improve training and implementation to mitigate civilian harm in future missions. Both internal and international inquiries have often explored, or attempted to explore, proportionality with respect to specific incidents.
Elder of Ziyon quotes a specific example in jurisprudence: a NATO attack on a Serbian TV station in which 16 people died. (The station was off the air for about a day.)
NATO Headquarters justified the bombing with two arguments; firstly, that it was necessary “to disrupt and degrade the command, control and communications network” of the Yugoslav Armed Forces, and secondly, that the RTS headquarters was a dual-use object which “was making an important contribution to the propaganda war which orchestrated the campaign against the population of Kosovo”. The BBC reported that the station was targeted because of its role in Belgrade’s propaganda campaign; RTS had been broadcasting Serb nationalist propaganda, which demonised ethnic minorities and legitimised Serb atrocities against them.
The International Criminal Tribunal for the former Yugoslavia (ICTY) ruled on the question:
It first questioned whether the station was a legitimate military target, and it decided that if it was used for command and control then it was, if it was only used for propaganda it wasn’t. It then goes on:
77. Assuming the station was a legitimate objective, the civilian casualties were unfortunately high but do not appear to be clearly disproportionate.[…]
79. On the basis of the above analysis and on the information currently available to it, the committee recommends that the OTP not commence an investigation related to the bombing of the Serbian TV and Radio Station.
In short: an attack on a propaganda TV station that may have had a dual use and that takes it off the air for one lousy day in exchange for 16 people getting killed is not considered “disproportionate” under international law. You can figure out for yourself what this ruling implies (a fortiori/קל וחומר) for IDF attacks on rocket launchers, arms caches, and infiltration tunnels, or targeted assassination of senior terrorists.
Back to Prof. Blank:
[A] note about another rule of proportionality. The international law governing when states may use force in self-defense (the jus ad bellum) also has a requirement of proportionality, but it is quite distinct (and serves a different purpose) from the law of war rule of proportionality discussed above. This jus ad bellum rule of proportionality mandates that a state acting in self-defense in response to an armed attack can only use force that is proportionate to the needs and goals of repelling or deterring the attack. This is not a “tit-for-tat” requirement, however, limiting the state acting in self-defense to only what its attackers did. There is no obligation of symmetry between the original attack and the force used in self-defense; indeed, the force needed to repel an attack may well be disproportionate relative to the the original attack, in order to stop it and deter continuing attacks. What it must be, instead, is proportionate to the ends of stopping and deterring the original attack and further attacks.
Go and read the whole thing.