self-initiated reprisal against an actual or alleged criminal, usually involving torture. During the Middle Ages in Western Europe, mob law existed in various forms: as club-law, the legalized self-initiated action allowed when court defense of a claim was denied, and a theme court, a tool for quick and merciless reprisals against the peasantry. Mob law, including ritual murder, was not infrequently the consequence of religious fanaticism skillfully roused by a church-backed belief in witchcraft.

Some forms of mob law have survived in modern bourgeois states. These forms include lynching in the United States, setting off bombs in public places, and planning accidents in transport vehicles.

Soviet law has established criminal responsibility in cases involving the moribund form of mob law known as the blood feud.