... continued from Monday.
So the ethic Jesus taught in relation to secular authorities was an "interim ethic," not in the sense of an ethic only for while he was on earth but only for the time before Jesus returned. There would be a time for confrontation of the worldly powers. But God would take the lead and now was not the time.
Neither Jesus nor any of the New Testament authors were addressing a situation where it was at all likely that believers would be able to transform the structures of society. The presumption of both what Jesus and the New Testament says is that you will be in the position of the weak and disempowered. Jesus' ethic is thus an ethic for the oppressed and powerless in society.
Even then, we should not assume that the specifics of the approach Jesus took at a specific time and place in history is meant to be the approach for all times and all places. Jesus largely advocated non-violent conformity to the will of the Romans. "If anyone forces you to go one mile, go with them two miles" (Matt. 5:41). "If anyone wants to sue you and take your shirt, hand over your coat as well" (5:40).
Walter Wink famously suggested that these were actually actions of non-violent resistance.  By responding in these sorts of ways, you shame the person. "If anyone slaps you on the right cheek, turn to them the other cheek also" (5:39). You thus force the person to strike you back-handed, an allegedly shameful way to hit someone.
Perhaps Wink captured a valid dimension of Jesus' rhetoric. But Matthew 5 puts these comments in the category of not getting revenge. The Old Testament Law says, "Show no pity: life for life, eye for eye, tooth for tooth, hand for hand, foot for foot" (Deut. 19:21). But Jesus says, by contrast, "do not resist an evil person" (Matt. 5:39), and the next paragraph is about loving one's enemies. The attitude Jesus advocates here is not one of defiance--not even non-violent defiance--but conformity with loving hope toward one's oppressor.
By the way, it is revealing once again that Jesus has the authority to modify Old Testament Law. The sequence in Matthew 5--"you have heard but I say"--is not simply a deepening of the law, as we saw in the previous chapter. Jesus modifies the Law in a substantial way. The Law says "Show no pity." Jesus says in effect that his "fulfilling of the Law" (Matt. 5:17), using the love commandment as the guide, shuffles and changes some of the Law. Here is another example where, at least on an individual level, the normal practice of Deuteronomy is negated. 
Jesus addressed a specific context in Galilee, although the Gospel of Matthew presumably wanted its audience to see this teaching as applying to them as well. However, we at least have to ask the extent to which Jesus' teaching on non-violent conformity was local or timeless and universal...
 E.g., Engaging the Powers.
 However, a key distinction is that Deuteronomy primarily targets a "civil" context. This is the context of societal justice. Jesus is addressing an individual context.