"When people begin to believe that organized society is unwilling or unable to impose upon criminal offenders the punishment they deserve then there are sown the seeds of anarchy - of self-help, vigilante justice, and lynch law. San Francisco experienced vigilante justice during the Gold Rush in the middle part of the last century; the mining towns of Montana experienced it a short time later; and it is still with us as a result of the series of unsolved slayings . . . ."
Vigilante justice
Behavior that resembles or matches that of vigilantes. Vigilante justice often describes the actions of a single person or group of people who claim to enforce the law but lack the legal authority to do so. However, the term can also describe a general state of disarray or lawlessness, in which competing groups of people all claim to enforce the law in a given area.