John Rawls
John Rawls was an American philosopher, a professor of political philosophy at Harvard University and author of A Theory of Justice (1971), Political Liberalism, Justice as Fairness: A Restatement, and The Law of Peoples. He is widely considered one of the most important English-language political philosophers of the 20th century. His theory of justice uses a device called the original position to ask us which principles of justice we would choose to regulate the basic institutions of our society if we were behind a 'veil of ignorance.' Imagine we do not know who we are - our race, sex, wealth status, class, or any distinguishing feature - so that we would not be biased in our own favour. Rawls argues from this 'original position' that we would choose exactly the same political liberties for everyone, like freedom of speech, the right to vote and so on. Also, we would choose a system where there is only inequality because that produces incentives enough for the economic well-being of all society, especially the poorest. This is Rawls's famous 'difference principle'. Justice is fairness, in the sense that the fairness of the original position of choice guarantees the fairness of the principles chosen in that position.
There are many other normative approaches to the philosophy of law, including critical legal studies and libertarian theories of law.
Read more about this topic: Jurisprudence, Normative Jurisprudence