"In the case of popular justice ... you have the masses and their enemies. Furthermore, the masses, when they perceive somebody to be an enemy, when they decide to punish this enemy - or to re-educate him - do not rely on an abstract universal idea of justice, they rely on their own experience, that of the injuries they have suffered, that of the way in which they have been wronged in which they have been oppressed; and, finally, their decision is not an authoritative one, that is, they are not backed up by a state apparatus which has the power to enforce their decisions, they purely and simply carry them out." Foucault, Power/Knowledge, pp. 8-9
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Of course, in that instance Foucault was not talking about capitalist justice--or, better put, the formal meting out of justice in capitalist societies--but "popular justice" or "peoples' justice" such as the kind Maoist groups at the time advicated. [If I recall correctly, what is here quoted is a response by Foucault to interview questions posed by a group that included some Maoists, and he was summing up how he interpreted their beliefs].
B.