Faith and State: Correlative Obligations?

I do see a qualification to "Thou Shalt Not Kill." It's called self-defense. What most states call "Just War," however, has nothing to do with self-defense. Certainly, Bush's military adventures in Iraq and Afghanistan have nothing to do with self-defense. At any rate, self-defense remains a legitimate qualification for all individuals--not just those individuals employed by the state. There's no double standard.

I do accept the Church's authority to interpret Scriptures. I concede I'm not clear on what obligation the Church's teaching authority on matters of faith and morals imposes on me as a political animal. Am I compelled to endorse a civil ban on contraception, artificial insemination and remarriage after divorce? In operational terms, must I favor a political system that sics the cops on people who contracept, artificially inseminate or remarry after divorce?

But we're straying from the main point. It's the double standard that sticks in my craw. If it's immoral for people to contracept, artificially inseminate and remarry after divorce, and the immorality of those activities compels a ban by the civil authorities, why would anyone exempt the civil authorities from that ban?

If it's immoral for people to steal, threaten and extort, why do we exempt the civil authorites from that ban? Why are they permitted to tax?