Romans 13:3

‘For rulers are not a terror to the good work, but to the evil. And would you have no fear of the power?'

And the logic behind this is that rulers are set up by God to control and prevent evil. Thus those who do good will have nothing to fear. It is only those who do evil who will be in terror of the authorities. And this is right, for in the face of justice all should be in fear of the consequences of doing evil. Paul was, of course, writing as one who had himself experienced the justice of Roman appointed governors, and was aware that on the whole Roman justice worked well. He does not deal with the case where the higher power is itself doing gross evil.