To live life under the sun is to live apart from God. And when we live life under the sun, pursuing the fullness of justice in this life, then we pursue what is vanity. Because as Solomon points out, in the place where justice is meant - namely the law courts - instead, very often, wickedness is found. Also, in the place meant to uphold righteousness - namely governments - instead, very often, wickedness is found. Our hope for justice must not be in life under the sun, but instead our hope for justice must be in the justice God. Yet, that too raises a question. Why doesn't God bring His justice, now? Why does He allow injustice to linger? Well, like with everything God does or doesn't do, He has a purposes. And in allowing injustice to continue He reveals something about mankind who lives life under the sun.
