vigilante

/vɪdʒɪˈlænti/

IPA: /V IH0 JH AH0 L AE1 N T IY0/

noun
  1. 1

    A person who considers it their own responsibility to uphold the law in their neighborhood and often does so summarily and without legal jurisdiction.

Source: https://en.wiktionary.org/wiki/vigilante