Vigilantes

Vigilantes are people who voluntarily carry out duties usually done by heroes without paying attention to the law. Due to the hero regulations people are not allowed to carry heroic duties out on their own and vigilantism is therefore forbidden.

History
According to All Might, the origins of heroes can be traced back to the vigilantes. When Quirks started to manifest there was no organization that controlled the Pro Heroes and they were therefore Vigilantes. Nowadays most of the vigilantes have vanished.

However, Knuckleduster, Pop Step and Gentle-Man had been active recently in their activities to help people and dispense justice as vigilantes. Aizawa stated that the Pro Heroes had never took action against them and left those three be so long they don't abuse their Quirks and go on a rampage.