The Christian's Attitude Towards The State (13:1-7).
Having called on Christians ‘not to be conformed to this world' (Romans 12:2), and having indicated that vengeance for wrongdoing lay in God's hands (Romans 12:19 - notice the use of ‘the wrath' in Romans 12:19 and Romans 13:5), and that Christians should be concerned to be at peace with all men (Romans 12:18), Paul now feels constrained both to affirm the need to conform with the systems of justice that were in place (as he had never intended otherwise), and to assure Christians that God was controlling justice through ‘God-appointed' justices. ‘Not being conformed to this world' must not therefore be seen as meaning that we are free from all the world's restraints. Indeed it rather means that we will see the authorities as have been placed there by God. For it is by them that God's present wrath is executed, and through them that the societies that they represent would know peace.
It is noteworthy that Paul nowhere else deals with this question. (Compare, however, where Peter does in 1 Peter 2:13 ff; 1 Peter 4:15 ff). That may have been because here he sees the church in Rome as at the hub of the Roman Empire, so that their attitude towards the government might be crucial in relations between church and state. Or it may be because he was aware of rumblings in Rome against the current political leadership, and did not want Roman Christians to succumb to them, with its consequent effect on the attitude of the authorities towards Christianity. The reference to paying taxes to whom taxes are due may suggest a connection with the tax rebellion by the inhabitants of Rome which, according to Tacitus, occurred in the middle 50s AD. But however that may be Paul, clearly considers it important to lay down advice on how to react to the Roman authorities.
Christianity at this stage mainly enjoyed the protection of Rome because it was seen as a branch of Judaism and thus as a religio licita, a religion whose rights were protected by the Roman Empire. This had been so from the mid 1st century BC when the Jews had been seen as allies of Rome, and not as a conquered people. They were thus free to practise their peculiarities (e.g. the Sabbath) without hindrance, protected by the Law. Christians, therefore, at this stage mainly enjoyed the same protection. (Even Caligula, although under strong pressure from advisers, forbore setting up his image in the Jerusalem Temple). It would only be later that the Roman authorities, sadly egged on by Jews, differentiated Christianity from Judaism thereby making Christianity a religio illicita, an unofficial religion that enjoyed no protection and that could be persecuted at any time.