By Michael Evans

The regulations covering alleged war crimes are complex, carefully worded and restrictive. The International Criminal Court (ICC) in The Hague does not appear to have jurisdiction in Gaza because the Israelis are not signatories to the Rome statute that set it up.

However, individuals and nongovernmental organisations from nations that are signed up can make a case to the ICC; and the United Nations Security Council can also pass a resolution calling for a war crimes investigation, as it did over alleged genocide in Darfur. In terms of the ICC statute, the use of white phosphorus could be governed by Article 8(2)(b) under which a war crime is potentially committed if weapons, including projectiles (shells), are launched "to cause superfluous injury or unnecessary suffering or which are inherently indiscriminate in violation of the international law of armed conflict".

It is up to Luis Moreno-Ocampo, the ICC chief prosecutor, to decide whether the allegations fall into line with the Rome statute definitions. Killing civilians is not a war crime in itself, unless there is an intentional attack directed against noncombatants or an assault is launched on a military objective "in the knowledge that the incidental civilian injuries would be clearly excessive in relation to the anticipated military advantage" - this is the principle of proportionality. In the case of allegations against British troops in Iraq, the ICC prosecutor decided the relevant criteria for starting a formal investigation had not been satisfied.

In the case of Darfur, it was alleged that thousands of civilians had been wilfully killed by the Janjawid rebels. Israel has always insisted that its aim was to target Hamas fighters, not Palestinian civilians.