Justice is an equal and opposite reaction sort of phenomenon. Justice is to human civilization what karma is to Indian religions: the glue that holds everything together. Take it away, and there is no structure around which to build any coherence.
Justice is, at its very core, an eye for an eye. When governments fail to recognize this, society suffers. If punishments are too stringent (e.g. a hand for a loaf of bread), fear and loathing grip the populace. If punishments are too relaxed (e.g. probation for burglary), fear and loathing grip the populace.
Justice acknowledges remorse and repentance, but is not fooled by crocodile tears. Remorse and repentance comes complete with a desire to make compensation for past wrongs, to makes amends to one's victims. A system that gives three strikes to the criminal without ever attempting to make the victim whole again leaves a society filled with victims who no longer trust their neighbors and criminals who are confident in their ability to escape meaningful punishment.
Justice pays an honest day's wages for an honest day's work. Justice demands that those with greater responsibility and special talent be better compensated than those with little responsibility and mundane talent. It also recognizes the connectedness of mankind and that super-aggrandizement of the few cannot be done on the backs of the many.
Justice protects the weak but disdains the lazy. It looks after the widows and orphans but derides the shyster and the sponge. When the hard working are asked to pay for the oppressed, they smile and comply. When the hard working are asked to underwrite the shirkers, they will kick over the traces.
Justice is not a fluid concept. It does not change over time, it does not move to fit society's perceptions.