Cluster bombs are not banned weapons. Cluster bomb units (CBUs) do not fall under any of the five 1980 Convention on Conventional Weapons (CCW) protocols, yet fear of non-detectable fragments of exploding CBUs was a driving force behind CCW Protocol I. “Although the effects of unexploded cluster bomblets are in some respects analogous to the effects of anti-personnel mines, they do not fall within the [CCW Protocol II] definition of anti-personnel mine…”  Some CBU variants are incendiaries that fall under CCW Protocol III, and unexploded CBU sub-munitions were a primary factor in CCW Protocol V’s adoption. Despite these close affinities to the CCW Protocols, CBUs are “conventional” weapons not addressed by the CCW.
Opponents of CBUs point to the CCW foundation treaty’s classic language “that the right of the parties to an armed conflict to choose methods or means of warfare is not unlimited” as an argument for their ban. Opponents’ concern centers on the high ratio of unexploded CBU sub-munitions, or bomblets, left on former battlefields to maim and kill civilians years after the conflict. NGOs disappointed by Protocol V’s outcome shifted their sights and joined forces with cluster bomb opponents, hoping that humanitarian impact could trump military utility.
“Employment of anti-personnel bomblets was not new. During World War I, the German Air Force employed the Splitterbombe, its 1kg…Ifl-Mäuse or Ilf-Bomben, for attack of enemy ground forces…”  In World War II, although the term “cluster bomb” had not been coined, the U.S. used hundreds of thousands of four-pound M-50 incendiary bomblets similar to later incendiary CBUs to set fire to lightly constructed Japanese cities. Approximately 330,000 Japanese civilians were killed, another 476,000 injured in those bombings.  By the time of the U.S.-Vietnam conflict, cluster bombs had been “perfected.” They have been used in all major conflicts since, including Gulf War I (1990-1991), and in the Former Yugoslavia. During the 2006 Israeli incursion into Lebanon against Hezbollah, Israel employed an estimated 4,000,000 CBU sub-munitions.
CBUs are bombs, or artillery rounds which, when dropped or fired, spin while in flight, opening at a predetermined height and rate of spin. Each opened spinning bomb canister disperses many, sometimes hundreds, of smaller sub-munitions, or bomblets, over a long and wide area of the ground. Dispersing like sand tossed onto a beach, each bomblet results in a relatively small but deadly and destructive detonation. CBUs used as area denial weapons are particularly effective against enemy infantry in the open, such as an attacking force of soldiers. There are incendiary CBUs, anti-personnel CBUs, anti-armor CBUs, runway-cratering CBUs, mine-laying CBUs, anti-electrical CBUs, leaflet CBUs, and combined-effects CBUs; they can be delivered by artillery, missile or aircraft – low flying fighters or high altitude bombers, via high-speed delivery or toss delivery. They employ contact fuses to explode on impact, air-burst fuses, or delayed-action fuses. Their military advantages are many.
A single U.S. 1,000 pound CBU may contain 202 bomblets, the bomblets often described in appearance and size as soft-drink cans or, in some models, hockey pucks or tennis balls. Bomblets are sometimes brightly colored to facilitate the location of duds, although children can be attracted to the colored objects, as well. The shape and size of the target’s footprint is determined by the pre-set spin rate of the dispenser, resulting in an elliptical footprint measuring as much as 1,600 by 1,100 feet – a target footprint roughly five football fields long and three football fields wide.
The problem with CBUs is their “dud” rate, the number of sub-munitions in each bomb, missile or artillery round that fail to detonate because of fuse or detonator failure. According to a manufacturer, the dud rate of one of the more widely used AP CBUs, the CBU-87, is about five percent, although some field reports put the rate at up to twenty-three percent.  Given the high number of CBUs used in Gulf War I, for example, NGO estimates of as many as 2,000,000 unexploded bomblets may be credible. Even though CBUs were never purposely used in or near populated areas, many dud bomblets were inevitably left on Kuwait and Iraqi battlefields. These explosives presented obvious problems of distinction and proportionality. Hundreds of civilians were reportedly killed or maimed for years after the conflict.
For years, NGOs, human rights groups, and the media protested the continued use of CBUs and called for their ban. The U.S. and Israel, only two of many States employing them, were most often the target of protests.  In 2008 the concerns of protesters had effect.
2008 Convention on Cluster Munitions.
In 2008, in Dublin, Ireland, the issue of CBUs was addressed by the Convention on Cluster Munitions, a multi-national treaty that bans cluster munitions.
The movement for a cluster bomb ban began in earnest in 2003, when the CCW’s Protocol V failed to restrict or ban them. Treaty negotiations commenced in Oslo in 2007 (the “Oslo process”), the final step of which was the Dublin Diplomatic Conference, in May 2008. Over a hundred States and numerous NGOs attended. The U.S., Israel and China were not represented. The Convention on Cluster Munitions, consisting of twenty-three articles, was agreed upon by 110 States. It is modeled on the Ottawa Convention on AP land mines, sometimes using the same language.
Under Article 1, Parties agree never to use, produce, acquire, transfer or stockpile cluster munitions. Excepted from the definition of cluster munitions are munitions that have fewer than ten sub-munitions, all of which have electronic self-destruction and self-deactivating mechanisms (Article 2.2 (c)). Article 3 require Parties to destroy their CBU stockpiles not later than eight years after the Convention goes into force, although a four-year extension may be requested.  A “limited number” of CBUs and sub-munitions may be retained for training purposes (Article 2.6.). Echoing CCW Protocol V, Parties to the Convention are required to clear and destroy cluster munitions remnants in areas under their control within ten years of the Convention’s entry into force (Article 4.1.), with renewable five-year extensions available (Article 4.5.). Article 5.1 is a novel provision, not included even in the Ottawa Convention, that requires State Parties to provide assistance to victims of cluster munitions, including medical care, rehabilitation, psychological support, and “social and Economic inclusion.” State Parties in a position to do so shall provide technical and financial assistance in implementing Convention obligations to other State Parties affected by cluster munitions (Article 6.2.) Article 9 requires Parties to impose domestic penal sanctions for activities prohibited by the Convention. Article 21 is also unique in that it encourages cooperation between States even if one of the States cooperated with is not a Party to the Convention.
As of this writing, ninety-six States have signed the Convention, five* have ratified it. States having the majority of cluster munitions have, so far, avoided the Convention, choosing instead to address the humanitarian impact of their weapons through the CCW. For the major powers, without a newer substitute weapon, CBUs are too effective a weapon to consider giving up entirely. For those States, questions of cluster munitions’ compliance or violation of distinction and proportionality will continue to be an issue and NGOs, human rights groups and media will continue to question their use of cluster munitions and, when they are used, their lawfulness.
For States retaining cluster munitions the issue of sub-munition failure rates must be addressed. CBUs can be manufactured with near zero dud rates, but the cost of a near-perfect weapon will be considerably greater. The U.S. addressed the unacceptably high sub-munition failure rate in a 2008 policy statement.
U.S. cluster munitions policy.
In July 2008, the Secretary of Defense announced a new U.S. policy on cluster munitions. After reciting the considerable combat benefits that cluster munitions provide, the statement notes, “Blanket elimination of cluster munitions is therefore unacceptable…” The announcement continues:
[T]he DoD policy establishes a new U.S. technical norm for cluster munitions, requiring that by the end of 2018, DoD will no longer use cluster munitions which, after arming, result in more than one percent unexploded ordnance…Additionally, cluster munitions sold or transferred by DoD after 2018 must meet this standard…As soon as possible, military departments will initiate removal from active inventory cluster munitions that exceed operational planning requirements…These excess munitions will be demilitarized as soon as practical…[T]hrough 2018, any U.S. use of cluster munitions that do not meet the one percent unexploded ordnance standard must be approved by the applicable combatant commander…
The statement concludes:
The new policy is viewed as a viable alternative to a complete ban proposal generated by the Oslo Process in Dublin…The new policy serves as the basis for the U.S. position in negotiations toward an international agreement at the U.N. Convention of Conventional Weapons…The United States has called for the completion of a new cluster munitions protocol…The CCW, unlike the Oslo process, includes all of the nations that produce and use cluster munitions, making any agreement reached there much more practically effective. 
The U.S. believes that a new CCW protocol, with a broad national involvement, will result in a cluster munitions agreement easier to comply with than the Dublin Convention. In any case, cluster munitions employed with care, and with a near-zero sub-munitions failure rate, are no more unlawful than artillery or high explosive bombs. While some weapons are per se unlawful – poisons, dum-dum bullets, serrated edged weapons – most often it is a weapon’s use that determines its lawfulness.
 Stuart Maslen, Explosive Remnants of War (Geneva: ICRC, 2000), 35.
 W. Hays Parks, “Conventional Weapons and Weapons Reviews,” 16 YIHL 55, 76, fn. 81
 The United States Strategic Bombing Surveys (Maxwell AFB, AL: Air University Press reprint, 1987), 92.
 Thomas M. McDonnell, “Cluster Bombs Over Kosovo: A Violation of International Law?” 44 Ariz. L. Rev. 31, 51 and 61 (2002).
 e.g., William M. Arkin, “America Cluster Bombs Iraq,” Washington Post (26 Feb. 2001); Thom Shanker, “Rights Group Faults U.S. Over Cluster Bombs,” NYTimes (12 Dec. 2003), A12; Isabel Kershner, “Israel Won’t Prosecute for Use of Cluster Bombs in Lebanon,” NYTimes (25 Dec. 2007), A4; “Cluster Bombs, Made in America,” NYTimes (1 June 2008), Wk 11.
 The Convention came into legal effect on 1 August 2010, six months after the thirtieth ratification or accession (Art. 17). As of 2 May 2011, one-hundred eight States have signed and fifty-six States have ratified this convention.
 U.S. Dept. of Defense News Release, “Cluster Munitions Policy Revised (July 09, 2008).
*This is an extract from: Gary D. Solis, The Law of Armed Conflict: International Humanitarian Law at War (NY: Cambridge University Press, forthcoming, Nov. 2009).
**Gary Solis is an expert on the law of armed conflict and is currently on the faculties of Georgetown Law School and the International Institute of Humanitarian Law in Sanremo, Italy. He is retired from the U.S. Marine Corps where he was a combat officer in Vietnam and later became a judge advocate. He set-up and headed the U.S. Military Academy’s course on the law of war. He has received several prestigious teaching awards including Phi Kappa Phi’s distinguished teaching award and the Apgar Award from the U.S. Military Academy. Besides his forthcoming book, Dr. Solis is the author of, “Marines and Military Law in Vietnam: Trial by Fire” and “Son Thang: An American War Crime”.