Therefore one must be in subjection, not only to avoid God's wrath but also for the sake of conscience. (ESV)
Obedience. It's a word that we probably do not like very much. That is the word that appropriately defines this idea of being in subjection. It is like a soldier's relationship with their commanding officer. Total obedience. Submission. Subjection. The Apostle Paul is describing our relationship with our government as one of us being in subjection.
Now, as hard of a pill as that might be to swallow, I want to give you another one to swallow. God wants us to be concerned with our attitude in the process. Consider the fact that both an atheist and a Christian can follow man's law. Both can be in total subjection. Christ wants his people to be obedient, but not just to avoid wrath, but for the sake of conscience. This speaks to our attitude.
Have you ever seen a child who obeyed their parents, but grumbled the whole time while doing it? Maybe they were told that they could not go to a particular event with their friends. They stayed home per their parents' instruction, but made the family's life miserable by complaining the whole time about how unfair the situation was. That is being in subjection, but not whole-heartedly.
God is always concerned about the heart. He is not just concerned about our actions. Consider the words God told to the prophet Samuel in the Old Testament: “For the LORD sees not as man sees: man looks on the outward appearance, but the LORD looks on the heart.” (1 Samuel 16:7, ESV) We need to make sure that what we do is sincere. Our heart needs to match our actions.
Do you want to please the Lord? Make sure that when you are acting in obedience to man's law you do so with a heart full of love. Ultimately, you are doing everything for the glory of God.