The Geneva Conventions on the Law of War, particularly common Article 3, prohibit the intentional killing of civilians. Common Article 3 prohibits:
"(a) violence to life and person, in particular murder of all kinds, mutilation, cruel treatment and torture;" and "(d) the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court, affording all the judicial guarantees which are recognized as indispensable by civilized peoples."
Other international human rights instruments, such as the International Covenant on Civil and Political Rights, state that arbitrary execution is unlawful.
Individuals who belong to the military wing of Hamas, such as Rantissi, are likely to be considered combatants. Individuals like Sheik Yassin, who was a quadriplegic and supposedly a spiritual rather than military leader, may be subject to more debate on their status as a combatants.
Targeted killings also implicate the Regulations annexed to the Hague Convention of 1907, which are widely viewed as customary international law. It is believed that most targeted individuals have been killed in helicopter strikes. The Hague Regulations prohibit the killing or wounding treacherously of individuals belonging to a hostile nation or army. [2] Killing or targeting particular individuals during an armed conflict is not illegal in itself under international law, nor is it accurately described as assassination, if the individuals are members of a hostile force. For example, the United States' targeted attack on Admiral Yamamoto during the Second World War was widely considered to be legitimate.
The key issue in deciding legality in such cases is whether or not perfidy or treacherous means were employed. The employment of treachery is what distinguishes assassination from a traditional killing. Killing individuals by a helicopter strike is generally an accepted tactic of warfare. More stealthy means, however, could be considered as acts of treachery.