Related Rule
Israel
Practice Relating to Rule 84. The Protection of Civilians and Civilian Objects from the Effects of Incendiary Weapons
Israel’s Manual on the Laws of War (1998) states:
Incendiary arms are not banned. Nevertheless, because of their wide range of cover, this protocol of the [Convention on Certain Conventional Weapons] is meant to protect civilians and forbids making a population centre a target for an incendiary weapons attack. Furthermore, it is forbidden to attack a military objective situated within a population centre employing incendiary weapons. The protocol does not ban the use of these arms during combat (for instance, in flushing out bunkers). 
Israel, Laws of War in the Battlefield, Manual, Military Advocate General Headquarters, Military School, 1998, p. 16.
Israel’s Manual on the Rules of Warfare (2006) states:
Conflagration weapons (flame-throwers, incendiary-bombs, phosphorous). Means of warfare involving incendiary devices are not prohibited (see discussion on the subject of phosphorous below) in themselves. The extensive range they can cover, however, means that the CCW Protocol [1980 Protocol III to the Convention on Certain Conventional Weapons] has been used to protect civilians and imposes a requirement for caution where conflagration weapons are used to attack a military target located within a concentration of civilians, and it is forbidden to blow up vegetation with incendiary devices, unless it conceals a military target. The Protocol does not forbid the use of these devices in battle (for example, for mopping up bunkers). 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 16.
The manual further states:
Phosphorous. Is phosphorous a banned weapon? Despite the accepted myths on the subject, phosphorous is not banned under the rules of warfare, because it is not considered to be a chemical weapon. A chemical weapon is a weapon intended to work on the systems of life and is constituted from a substance that causes a chemical reaction in the body expressed in such symptoms as asphyxiation, burning, weeping, etc., whereas phosphorous is an element in nature which reacts to the oxygen in the air by catching fire. In that respect, phosphorous is no different from petrol (gasoline) reacting to a lighted match, and what differentiates it from chemical weapons is that its reaction is not directed against the human physiology in particular, it will burn whatever it touches. 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 19.
In addition, the manual states: “Phosphorus is permitted for use, as long as its use is directed against combatants and not against civilians.” 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 50.
(emphasis in original)
The Manual on the Rules of Warfare (2006) is a second edition of the Manual on the Laws of War (1998).
Upon accession to the 1980 Convention on Certain Conventional Weapons, Israel stated:
With reference to the scope of application defined in article 1 of the Convention, the Government of the State of Israel will apply the provisions of the Convention and those annexed Protocols to which Israel has agreed [I, II and III] to become bound to all armed conflicts involving regular forces of States referred to in article 2 common to the Geneva Conventions of 12 August 1949, as well as to all armed conflicts referred to in article 3 common to the Geneva Conventions of 12 August 1949. 
Israel, Declarations and statements of understanding made upon accession to the Convention on Certain Conventional Weapons, 22 March 1995, § a.
In 2009, in a report on Israeli operations in Gaza between 27 December 2008 and 18 January 2009 (the “Gaza Operation”, also known as “Operation Cast Lead”), Israel’s Ministry of Foreign Affairs stated:
Use of Munitions Containing White Phosphorous
406. During the Gaza Operation, IDF [Israel Defense Forces] forces used munitions containing white phosphorous, which is in common use by militaries worldwide. In particular, IDF used two different types of munitions containing white phosphorous – exploding munitions and smoke projectiles.
407. Exploding munitions containing white phosphorous. A small number of exploding munitions containing white phosphorous were used by the IDF during the Operation as mortar shells fire by ground forces and as rounds from naval vessels. These munitions were fired only at open unpopulated areas and were used only for marking and signalling rather than in an anti-personnel capacity. … No exploding munitions containing white phosphorous were used in built-up areas of the Gaza Strip or for anti-personnel purposes. The restrictions on the use of incendiary weapons under Protocol III (relating to Incendiary Weapons) to the [1980] Convention on Certain Conventional Weapons (“CCW Protocol III”) were observed at all times, even though Israel is not a party to the Protocol (for further elaboration, see below).
408. None of the instances in which exploding munitions containing white phosphorous were used by the IDF during the Gaza Operation has given rise to particular criticism. Still, on 7 January 2009, although not required under international law, it was decided as a precautionary measure, in order to minimise the risk to civilians, that the IDF would cease to use such exploding munitions during the Gaza Operation. IDF forces fighting in Gaza were instructed to act accordingly.
409. Smoke projectiles containing white phosphorous. The second and main type of munitions containing white phosphorous employed by the IDF during the Gaza Operation was smoke screening projectiles. …
410. … [S]moke-screening projectiles are designed to create a protective smoke screen for battlefield purposes, and were used exclusively for this purpose by the IDF during the Gaza Operation. The smoke projectiles may, on occasion, produce incidental incendiary effects, but this does not make them incendiary weapons for purposes of international law.
International Law Applicable to the use of Incendiary Weapons
411. The use of munitions containing white phosphorous is not prohibited by any international treaty, including CCW Protocol III. Article I of CCW Protocol III defines “incendiary weapon” as “…any weapon or munition which is primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat, or combination thereof, produced by a chemical reaction of a substance delivered on the target.” Article I further expressly excludes from its purview: “… Munitions which may have incidental incendiary effects, such as illuminants, tracers, smoke or signalling systems.”
412. Accordingly, although Israel is not a party to CCW Protocol III, it is clear that the use of munitions containing white phosphorous as a smokescreen is not regulated nor prohibited by it.
414. Although the use of weapons containing white phosphorous for smoke-screening purposes is not prohibited by any international treaty, it is still subject to the applicable norms of the Law of Armed Conflict, including the principles of distinction and proportionality, which regulate the employment of any types of weapons during an armed conflict. 
Israel, Ministry of Foreign Affairs, The Operation in Gaza 27 December 2008–18 January 2009: Factual and Legal Aspects, 29 July 2009, §§ 406–412 and 414.
[footnotes in original omitted]
In January 2010, in an update of its July 2009 report on Israeli operations in Gaza between 27 December 2008 and 18 January 2009, Israel’s Ministry of Foreign Affairs stated:
117. This investigation dealt with the use of weapons containing phosphorous by IDF forces during the Gaza Operation. The investigation focused on the different types and number of weapons containing phosphorous used during the Operation, the purposes for which they were used, the applicable professional instructions and rules of engagement, and the extent of compliance with those instructions and rules. …
118. The Military Advocate General reviewed the entire record of the special command investigation. With respect to exploding munitions containing white phosphorous, the Military Advocate General concluded that the use of this weapon in the operation was consistent with Israel’s obligations under international law.
119. With respect to smoke projectiles, the Military Advocate General found that international law does not prohibit use of smoke projectiles containing phosphorous. Specifically, such projectiles are not “incendiary weapons,” within the meaning of the Protocol on Prohibitions or Restrictions on the Use of Incendiary Weapons [1980 Protocol III to the Convention on Certain Conventional Weapons] because they are not primarily designed to set fire or to burn. The Military Advocate General further determined that during the Gaza Operation, the IDF used such smoke projectiles for military purposes only, for instance to camouflage IDF armour forces from Hamas’s antitank units by creating smoke screens. 
Israel, Ministry of Foreign Affairs, Gaza Operation Investigations: An Update, 29 January 2010, §§ 117–119.
[footnotes in original omitted]
In July 2010, in a second update of its July 2009 report on Israeli operations in Gaza between 27 December 2008 and 18 January 2009, Israel’s Ministry of Foreign Affairs stated:
The use of smoke-screening munitions containing phosphorus during the Gaza Operation was also addressed in a special command investigation dedicated to the issue. This investigation determined that the policy of using such munitions was consistent with Israel’s obligations under the Law of Armed Conflict. Nonetheless, following that investigation, the Chief of the General Staff ordered the implementation of the lessons learned from the investigation, particularly with regard to the use of such munitions near populated areas and sensitive installations. As a consequence, the IDF is in the process of establishing permanent restrictions on the use of munitions containing white phosphorus in urban areas. 
Israel, Ministry of Foreign Affairs, Gaza Operation Investigations: Second Update, 19 July 2010, § 97.