"If men were angels, no government would be necessary," says James Madison (The Federalist Papers, No. 51).
"Wrong!" says Thomas Aquinas. "A man is the master of a free subject, by directing him either towards his proper welfare, or to the common good. Such a kind of mastership would have existed in the state of innocence between man and man." Thomas gives two reasons. First, man is a social being, and social life cannot exist if there is not someone to look after the common good. Second, it would not be fitting for one person to surpass another in knowledge and virtue unless the one with the greater gifts used them for the benefit of others, citing 1 Peter 4:10 (Summa Theologiae, I, Q. 96, Art. 4).
In the Christian view, government is not a result of the Fall. Proper order and authority is built right into God's design for creation.