"Justice" is said in many ways. Yes, it tends to be normative; however, values can be weighed against one another. I value candy, but "I should seek candy" is far from tautological. Justice, in particular, rides rather far down my hierarchy of values.
Your decision making works as a value scale, morality not so much.There is a subset of actions you can take which are just. If you do not give a high weight in acting justly, you're a dangerous person.
Cass Sunstein, David Schkade, and Daniel Kahneman, in a 1999 paper named Do People Want Optimal Deterrence, write:
If we're after optimal deterrence, we should punish potentially harmful actions more if they're hard to detect, or else the expected disutility of the punishment is too small. But apparently this does not accord with people's sense of justice.
Does this mean we should change our sense of justice? And should we apply optimal deterrence theory to informal social rewards and punishments, such as by getting angrier at antisocial behaviors that we learned of by (what the wrongdoer thought was) a freak coincidence?