Israel has tragically suffered recently from a “wave of terrorism” by terrorists wielding knives and guns. Soldiers and citizens alike have bravely fought back against these assailants, significantly reducing the casualty toll.Frequently, the terrorists were killed by these acts of self-defense, which remain morally justified while the terrorists represent a danger. In a few cases, however, bystanders continued to attack the terrorists even after the threat had been clearly neutralized (i.e., the terrorist was lifeless or subdued), raising heated debate within society whether these were justified acts of vengeance. While I have no sympathy for these ruthless terrorists, I believe that Jewish law does not permit such action.Jewish law prohibits the intentional killing of innocents, both Jewish and non-Jewish alike. This prohibition was included in the seven Noahide laws and reaffirmed even after God elected a “chosen people” and gave them the Torah. There are times, however, when a person may kill someone else, as in cases of mandated warfare or acts of self-defense.The right to self-defense is exemplified within Jewish law by the law of rodef (the pursuer).The Sages contend that the verse “You shall not stand idly by the blood of your neighbor” not only demands saving a friend from drowning or from a hungry lion, but further dictates stopping an assailant from committing murder. This mandate was extended to both threatened victims and bystanders alike. It further includes cases in which a generally righteous person is unjustifiably attacking a known miscreant, or if a Jew is assailing a non-Jew.Jewish scholars debated what guidelines might be issued for those trying to stop the assailant. Some believed that the rescuer may kill at all costs under all circumstances because the attempted murderer has, as it were, abdicated his right to life by making himself subject to the laws of rodef.Yet the normative law asserted that when possible, one must use a less lethal method, such as cutting off a hand or debilitating the legs. A few scholars proposed an intermediate position that would permit the intended victim alone (as opposed to bystanders) to always use lethal force, but this position did not gain widespread currency.Some figures, including Rabbi Ya’acov ben Asher, believed that a person is even liable for murder for using excessive force in stopping the pursuant. Maimonides, however, deemed it a serious sin worthy of “heavenly punishment” but not warranting penalty from a judicial court.Some explained that Maimonides felt it was unfair to punish someone who was rushing to stop a murder, even though he could have limited the harm to the assailant. As such, if he was warned on the spot that he was using excessive force, but killed the assailant anyway, he would indeed be liable for murder.Others asserted that while the rescuer erred, Maimonides believed that we should not punish someone for killing an assailant who ultimately brought his death upon himself.Of course, no one expects a citizen or even a security officer who has moments to act to calculate exactly how much force might be necessary to stop an assailant.This would be utterly unreasonable and would prevent people from acting to save the victim. (For similar reasons, the Sages decreed that a rescuer does not pay for property damage that he causes during his act of heroism.) Moreover, it is not always easy to know when a threat has been fully neutralized, especially when a wounded terrorist continues to struggle. Nonetheless, once the assailant is clearly incapacitated, one is not allowed to kill them, whether out of a sense of vengeance or vigilante justice.During the recent violence, rabbis Shmuel Eliyahu and Moshe Tzuriel have contended that these terrorists should be treated not as regular assailants but as enemy soldiers who may be killed. Rabbi Benzion Mutzafi went so far as to assert that we should punish those who keep them alive! Yet even if we assume that lone-wolf attackers should be treated as enemy soldiers (and not regular assailants), it’s unclear why they retain that status once they’ve been captured or debilitated. Should we kill enemy soldiers who wave a white flag on the battlefield? Why not wipe out the jail cells of all convicted terrorists? Eliyahu argued that these assailants might ultimately go free and return to terrorism.Yet the proper response to that problem is to stiffen jail terms and not engage in lopsided prisoner swaps that free murderers.In any essay published many years ago, Rabbi Yehuda Henkin (whose son and daughter-in-law were tragically killed in this wave of terrorism) further noted that killing a captured enemy combatant goes against international norms and would thus constitute a hillul Hashem, a desecration of God’s name. Moreover, as Rabbi Yaakov Ariel recently noted, the inevitable recording of such executions might further enrage our enemies and add to the threats against us. Ariel has also argued that while military assassinations are sometimes necessary, those decisions must be made by military experts, not vigilantes. Indeed, the danger of citizens taking the law into their own hands has been tragically displayed by brutal attacks on innocent bystanders who were mistaken for terrorists.Perhaps the most cogent argument has been issued by Rabbi David Stav, who beseeched us not to descend to the moral depravities of our enemies by killing unnecessarily.The goal of our nation is to execute justice, not captured prisoners. The writer teaches at Yeshivat Hakotel, directs the Tikvah Israel Seminars, and is a junior scholar in the Judaism and Human Rights project at the Israel Democracy Institute.