J.D.’s post immediately below has stimulated a spirited discussion, but missing from the debate is an accurate understanding of several key elements of the law of war.

First, there are two ways weapons can be unlawful. The obvious answer is if they are the subject of a specific prohibition, either a treaty provision such as the four protocols to the 1980 UN Convention on Certain Conventional Weapons (CCW), or a customary international law ban. A treaty provision, such as the Third Protocol to the CCW on Use of Incendiary Weapons, widely discussed in the comments to J.D.’s post, is normally binding only on the actual parties to the agreement until such time as it might become so widely recognized that it takes on the status of customary international law. Weapons generally recognized as now banned under customary practice include among others, poison, chemical and biological weapons, expanding bullets, and weapons wounding by non-detectable fragments. Despite frequent U.S. claims to the contrary, the rest of the world does not agree that the actions of the most militarily powerful states determine customary international law; under general principles of international law states enjoy a sovereign equality, so a customary norm can be established despite U.S. practice to the contrary. But international law also generally recognizes that “consistent objectors,” states which have not ascribed to a norm from before the time it is considered to have achieved customary status are not bound by that particular norm. So the U.S. objection to CCW Protocol III could logically keep those provisions per se from being binding on it even if they were considered to have reached the status of customary international law.

The second way a weapon can be unlawful is if its use would violate general principles against means of war causing “superfluous injury” or “unnecessary suffering,” a concept dating from the 1868 St. Petersburg Declaration on Exploding Bullets and now widely recognized as constituting customary international law. These principles can result both in the outright illegality of a weapon, as well as more limited restrictions on certain uses. For example, while exploding or incendiary bullets of less than 400 grams (14 oz.) were banned outright by the 1868 Convention, it was recognized during WWI their use was essential for the aircraft of the day to shoot down Zeppelins bombing English cities, and the prohibition is now recognized as banning simply their deliberate anti-personnel use. So they can lawfully be fired at an aircraft, as long as the aircrew are not the deliberate aimpoint. It is thus consistent with customary law to assert that white phosphorous (WP) can lawfully be used for smoke screens, to ignite military stores, etc., but not as a weapon of choice against enemy combatants unless no other weapon can reach them. This is exactly the conclusion the recent ICRC study on Customary International Humanitarian Law reached; Rule 85 states: “The anti-personnel use of incendiary weapons is prohibited, unless it is not feasible to use a less harmful weapon to render a person hors de combat” while the previous Rule 84 calls for particular care to avoid or minimize the impact of incendiaries on civilians.

The article in the Army’s own artillery journal leaves no doubt that WP was deliberately employed in an anti-personnel role in Fallujah; the core legal issue concerning its use against the Iraqi fighters thus becomes a factual question of whether other weapons causing less superfluous injury or suffering could have been employed. If so, its use in that role was illegal, if not then it was permissible against the enemy fighters.

The legal issue that I think should be of more concern, however, relates to the overall protection of the civilian population. But here the proper question is larger than simply the use of WP, it is the legality of artillery fires at all against an urban area reasonably knowable to still contain large numbers of civilians. The law of war is quite clear that armed forces must distinguish between military and civilian objects in conducting attacks; this principle of distinction requires situation specific consideration of the means and methods to be employed. According to the account of the Army artillerymen, virtually all the artillery firing against Fallujah was conducted in a “danger close” environment, meaning U.S. forces were within 600 yards of the intended targets and the first rounds of each fire mission would thus be deliberately offset from the target in a direction away from friendly forces and then walked on using observer spots. This is necessary because according to this source dispersion, or essentially notional first round accuracy, of the Palladin howitizers employed at Fallujah is +/- 370 meters! That means that the first round could predictably fall anywhere within four football fields of the intended target. That’s not really a problem in warfare in open terrain, but in an urban environment it surely is.

Cynics argue that the law of war is crafted in such a way as to allow military officials to justify almost any conduct as lawful. It is certainly true that most of these norms were crafted to reflect the practical necessities of war, but there are clearly occasions where the law requires refraining from militarily preferred courses of action. I think a strong case can be made that the use of non-precision guided artillery fire against specific insurgent positions in a city which still contains substantial numbers of civilian persons is one of those tactically desirable options that is simply not permissible. To be lawful for urban use today, I believe that precision guided or short-range munitions, capable of first round impact within a few meters of the intended aimpoint, are required regardless of the actual type of warhead employed. The unfortunate reality of this conclusion is that attacks might need to be conducted in a manner that would require taking more friendly casualties than the use of long-range firepower would, but it is simply legally and morally wrong to assume that we can kill any number of civilians necessary to spare American lives; particularly where our purported purpose is to "liberate" those very civilians.