Jesus taught that we should keep praying until an answer comes. We have learned to be persistent in getting help from lesser powers. Why not appeal to Heaven?
This is a parable. It was not an actual widow and judge, but a fictitious story designed to teach a universal truth to those who heard it.
There’s no doubt that we should be people of social justice. Jesus’ teachings about loving our neighbouring, healing the sick, visiting prisoners, releasing slaves and sharing our food with the hungry exemplify Christian living.
We are to live oppositely to whatever injustice is happening.
Paul added that all the good ways we try to help must flow out of sincere love for the people. Otherwise, social justice is just pompous attitude and noise pollution.
I am always intrigued by Jesus’ apparent lack of retaliation against the Roman government. Instead, his correction was used with laser aim against heartless religion. Perhaps the story of the Widow and the Unjust Judge point us in the direction of Godless government.
One other bit of cultural background helps us understand the account. In a civil dispute the judge would be responsible for dealing with the woman's claims. Since she is alone, if she is to find justice, the judge must supply it. Although the judge is not known for his compassion—he neither feared God nor cared about men—he still is responsible to hear her case.
In Corinth, Paul advised against taking a spiritual brother to court. It’s better if the church can work out a peaceful solution. Apparently the civil justice system is not as merciful or redemptive. There is not the same commitment to love that we should find in God’s Kingdom.
But, instead of writing off earthly government, Paul says we are to do two things. First, we are to submit to those who rule in these matters and secondly, we are to pray for the powerbrokers and decision makers.
In this parable of the Unjust Judge, we get a glimpse into politics. The Judge finally gives the woman justice because she kept coming back requesting it. The heartless Judge finally helps to save face and to get her off his back. All the while, she was truly vulnerable in society and had no one else to resolve her matter.
In the parable of the Widow we are reminded that we need a better system than the world provides. If you are healthy and secure in life, you may not see yourself as a widow or orphan. But chances are you will find yourself alone without support at some point in your life. If I die before my wife, she will be a widow. When my parents die, I will be an orphan. When I am vulnerable and helpless, where will I turn? You are never too young or old to be a widow or an orphan.
It would be a mistake to assume that the woman in this story is old. In the ancient culture, women married in the early to mid teens, and the life expectancy for men who reached adulthood often did not exceed "thirty-something" (Jeremias 1972:153). Yet being a widow, she was among the most vulnerable people in her society. 
Governments often fail to care for the most vulnerable members of society. The Kingdom of God is called to seek out and love the ones who have no justice. In so doing, we are the countercultural family constantly adopting helpless citizens into our house.