Exploring the Origins of Government

I was recently reading a portion of a book wrote by Charles Colson, and in it he stated that human government was instituted by God in order to restrain human sin and preserve order. I have heard this type of belief stated many times before, but in the past few years I have wondered whether it is really true. I have also begun to question where in scripture people like Colson get this line of reasoning.
Colson used the example of God placing an angel at the entrance to the Garden of Eden to show that government was divinely instituted. But this example doesn't illustrate his point at all! It does show that God is the ultimate governing power. It shows that He intervenes in human affairs when He pleases. But it has nothing to do with human government.
Several months ago, I had a discussion with a local pastor who argued passionately from Genesis 9:6 that human government was set up by God. This is what that verse says, "Whoever sheds man's blood, by man his blood will be shed; For in the image of God He made man."
This verse seems to have slightly more relevance than Colson's analogy, but still says little regarding our topic. Jesus said a very similar thing to this in the gospel of Matthew, "All who draw the sword, shall die by the sword." It seems that the Genesis text is laying out this principle for the first time. Those who tend toward a violent lifestyle, tend to die in violent ways. Jesus' later reference to this passage has no immediate reference to human government.
The various passages that some people bring up to support this assertion that God ordained and set up human government seem very weak and shaky to me. Do any of you know of better scripture supporting this? What do you think of this idea? You may ask me what or who did set up government if God did not.... well, we'll get to that later, lol. Let's look at this first question thoroughly first.