The fact is Israel retaliates against acts of war coming from the Palestinians with aggression only after prolonged periods of belligerence. Many people have told them to retaliate one on one, so if the Palestinians fire a rocket Israel replies with a rocket. If they use chemical/biological weapons then Israel replies with the same.
Here you go Article 17 covers it in detail
The burden when it comes to protecting civilians from the combat effects of war falls on three distinct parties: First, the advancing force, which must make every effort to avoid unnecessary harm to civilians. Second, the defending force, which may well have the best chance at removing civilians from the area before it actually becomes the scene of combat. Third, and most important, the civilians themselves. They must avoid participating in the fight. In fact, they should simply avoid, if possible, being in the area where the fighting occurs.
There is no obligation to evacuate civilians from the battle area. At the same time, deliberately endangering noncombatants is a violation of the laws of war. In practice, commanders often avoid the problem of civilians in the battle area by simply giving a warning. This might be accomplished by dropping leaflets, or by making announcements over loudspeakers or radio. At first glance, such a practice might seem unlikely or even blissful. But, as a military matter such warnings make sense (unless, of course, surprise is a factor). First, the commander giving the warning is making a demonstrable effort to avoid harming noncombatants. Second, as a military matter, a warning to civilians that they should remove themselves from the area has the propaganda effect of reminding them that their own military force may be unable to stem the advancing forces. Third, most civilians will move toward their own forces and not their enemy. When that occurs, their own forces may well be presented with a major logistical and tactical problem.
