Justice can only be individual and specific.
Justice is, in a sense, the opposite of love. When you have love, nothing else matters. When you don't have justice, nothing else matters.
Justice is, generally, things being as they should be. Because it is usually an attempt to balance the past, it is usually Impossible (reparations in particular), therefore justice is properly understood as a direction, not a destination. As close as Justice as it's possible to get is called Fairness.
Law is explicitly a guideline for the ignorant. If the law allows harmful acts you still have an ethical responsibility to not do harm. If the law forbid harmless acts, that's called tyranny and you still have the right to do them. When you know better than the jaw, that is how you should behave, and when you're in a new situation you should follow the law until you have Reason to act otherwise.
You have a moral responsibility to understand right and wrong and the law's relationship to it because you have a moral responsibility to yourself to make the best decisions you can in every situation. To be an ethical agent requires being actively educated about ethics and that's a prerequisite for legitimate citizenship.
There are three parties to a wrongdoing; the wrongdoer, the victim(s), and society. The wrongdoer is served justice through redress (losing any benefit they got from the act). The victim(s) is served justice through restitution (being returned to the position they would have been in of the act didn't happen). Society is served justice through rehabilitation (reasonable certainty that the act won't happen to someone else). There is no room for retribution or revenge in justice. Even if it is the only way to do restitution, wanting to cause harm to another is still a failure of society's ethics or a mental illness.
Justice is, with honour and love, one of the primary reasons for living. Most forms of meaning can be understood as one or some combination of them.
The legitimacy of a society rests on caring for the best interests of every creature in its jurisdiction. That's the cornerstone of Justice. In terms of government, that means treating every individual as an individual, not special interest groups, not even the majority.
Social justice is an oxymoron. Every person has a unique embodied perspective on the universe with all the unique experiences and understandings that entails. There are as many differences between people in a social group as there are between the average of their group and the average outsider. Group justice would be an impossible calculus even if it was morally permissible.
Procedural Justice means that the rules are fair; simple, necessary, reasonable, adequate, equally accessible and applied. It requires due process in business as well as government. It requires transparency and accountability for government and privacy and freedom for citizens.