The people of Israel and Judah have fallen. They weren't always this way. They were righteous. Isaiah is reminding them where they were and how they used to be, telling them that they can be like they were before, if they repent:
They were
They were faithful
They were full of justice
They were righteous
But now
They are murderers
They are corrupt
They steal and take bribes so that there is no more justice.