My understanding of vigilantism is that it constitutes any act motivated by a desire to seek justice outside of the state-enforced judicial system. As such, can one be considered a vigilante if one's personal conception of justice doesn't match up with what the majority generally considers to be justice?
In Edgar Wright's Hot Fuzz, for example, the Neighbourhood Watch Alliance murder those that they feel ruin their village's chances of winning village of the year. They're the villains of the film, but they claim to do what they do "for the greater good", so presumably from their point of view they've been punishing those that break the rules they've established for the town. The rules are bizarre, but they're rules nonetheless, and so, from a warped perspective, punishing those who break them could be considered a kind of justice.
With this in mind, could the Neighbourhood Watch Alliance be considered 'vigilantes', albeit villainous ones?
Edit: I think its worth clarifying - I mean more to ask whether the justice that an individual seeks has to be the one advocated by the state (as in nation-state, rather than US state), or could it be their own personal idea of justice? Does a vigilante have to uphold existing laws, or can they uphold their own?