Justice (n.) is not an abstract general standard by which human reason assesses social practices and institutions, it is rather a standard by which a mode of production measures itself. It is a juridical concept measuring not, for example, if capitalism is just, but whether this or that is just within the logic of capitalism.
Justice (n.) is not and cannot be a genuinely revolutionary notion. The revolutionary who is captivated by the passion for justice misunderstands, in the marxian view, both the existing production relations and his own revolutionary aspirations.
Justice (n.) is the property a transaction possesses when it stands in a certain functional relationship to the mode of production in which it takes place.
Justice (n.) lies, for an economic transaction, not in natural law but in its fit with the mode of production: slavery is unjust on a capitalist basis; so is cheating on quality.
Justice (n.) is in its turn reduced to the actual laws.