The Mishna (81b) offers examples of situations where the Jewish court cannot act, but kana’im pogim bo (“zealots strike him”) – it would be acceptable for an individual who is offended by the situation to step forward and take the law into his own hands.
The prime example of this behavior is the case of Pineḥas (see chapter 25) who stepped forward and killed Zimri ben Salu, a prince from the tribe of Shimon who was engaged in idolatrous harlotry with Cozbi bat Zur, a Midianite woman. The Gemara on today’s daf offers a detailed midrashic explanation of the interaction that took place.
According to the Gemara, the tribe of Shimon, whose members were being judged and killed by Moshe for their activities with the daughters of Mo’av and its gods, approached Zimri and demanded that he act to defend them. Zimri then took a group of 24,000 of his men and approached Moshe while bringing with him Cozbi bat Zur. His argument to Moshe was that if she was forbidden, how could Moshe’s wife, Zipporah the daughter of Yitro, the Midianite priest be permitted? Stung by this argument, Moshe had no response, and they stood crying until Pineḥas stepped forward.
According to Rav Ḥisda, the law of kana’im pogim bo is unique in that someone who asks for a halakhic ruling whether they can take the law into their own hands will not be given permission to do so – the law applies only if the person does it on his own initiative. The Talmud Yerushalmi goes so far as to say that doing so goes against the wishes of the Sages and that had God not supported the actions of Pineḥas he would have been censured by the leadership. Furthermore, as Rabba bar bar Ḥana points out in the name of Rabbi Yoḥanan, had Zimri defended himself and killed Pineḥas he would not have been considered a murderer, since he had every right to defend himself.