This subject will keep us going for a long time, and has kept others going for even longer.
The reason, in my eyes, that justice seems to be adapted as you mention, Butterfly, to the society or moment it applies. Justice should be applied all the time the same way.
Now, imagine, you buy a new stereo, tv or what ever. The first thing you do when you get it home is after ofcourse unpacking it, look at the instruction book. You want to know how to install it. Right?
But, but ,but. God has given us several "instruction books" as well. The first one were the Tables, via Abraham and with an verbal update via Moses handed to the Jews.The Christian received an other verbal update thru Jesus. Some Popes wrote, many years later, their version of what God's message had been (the Bibel & New Testament). Between Abraham & Mohammed (may peace be upon them)there were many different Profets from different cultures & countries. They all tried to pass on the message from God. The last Profet, Mohammed(PBUH) received an other set of messages from God, that he was supposed to pass on to the people of this world. He realized quickly that this message was garbled and misquoted very quickly. So he decided, while he was alive, to write it down.This is the Quran. So as you can see it is basically everytime the same message. The only one in it's original form is the Quran. That is why this is the most explanatory, cos like in real life. The first instruction manual that came with the first TV is different than the manuals we see today. Today they have much more info. The same goes for the last of God's messages.
So, it does not really matter which religion you follow as long as you worship God alone, and no statues etc.
As long as you live a "good" life, be good, do good have integrity, don't lie, don't cheat etc etc God will love you and reward you.
Reglion is like a way of living according to these rules & instructions. This give us a sense & direction in life.
But as you look around you you can see that religion is not very much present anymore, specially in the Western world. When I was young, we had religious study in school. But now, reglion is banned from State schools in most countries. As the French say - systeme lalique-
So how many people grow up and have grown up without knowing the rules and regulations? Or if they know them, it is not "fashionable" anymore to follow them. Or they forget the basic rule. Life on Earth is like a passage only. But Justice is justice, here on Earth and in the "devine" world. One is carried over to the next.
I am sure that if all of us could convince the rest of the world to look at justice this way, we would have a really good world to live in.
Did I make sense?
Regards

Aisha-Taweela