Justice has always attracted as much serious attention as utility in the theory of ethics. Economics is not ethics-free: “…basing economics on the ethics of individuals assumed to be entirely self-interested can go badly wrong, and that ‘willingness to pay’ is invalid as a means of valuation” (Broome, 2008).
Social justice is proposed in Rawls’ theories of justice and fairness (1971, 2001). His principles of justice are:
(1) “Each person has the same indefeasible claim to a fully adequate scheme of equal basic liberties, which scheme is compatible with the same scheme of liberties for all”; and
(2) “Social and economic inequalities are to satisfy two conditions: first, they are to be attached to offices and positions open to all under conditions of fair equality of opportunity; and second, they are to be to the greatest benefit of the least-advantaged members of society (the difference principle).”
Broome, J. (2008) “Why Economics Needs Ethical Theory”, in Kaushik Basu and Ravi Kanbur (eds.), Welfare, Development, Philosophy and Social Science: Essays for Amartya Sen’s 75th birthday, Oxford: Oxford University Press. PDF available here.
Murphy, R. (2015) “The Joy of Tax. How a fair tax system can create a better society”, Random House, ISBN: 1473525330, 9781473525337. Available on Google Books.