I just read a piece where the Vatican has denounced the execution of Saddam Hussein. The argument was simply that it was punishing one crime by committing another. One of the things I am particularly thankful for is the way that the Lutheran Symbols distinguish between the two kingdoms and the two swords. The papacy across the years has had a fatal tendency to confuse the two - and there was certainly a time when the Bishop of Rome claimed that both swords and kingdoms were his by virtue of being Christ's vicar upon earth. The Lutheran Church's clarity on this perennial and vexing question needs to be heeded more.
To the government God has given the sword, and its task with that sword is to punish evil doers. That is not by any stretch of the imagination to suggest that the government has never abused the sword entrusted to it. It has indeed, time and again. And when it does, the Church is perfectly right to call the government to repentance. But what the Church can never do is insist that the government govern by the sword of the Spirit entrusted to HER.
The Gospel rules in the Church, but natural law rules in the state. If we visit the scene of our Lord's crucifixion we will note the vital difference between the two swords, the two kingdoms. The "good thief" - the one who confessed Christ and asked for our Lord to remember Him in His kingdom - did indeed receive remission of sins, the promise of paradise given to him that very day from the lips of our dying Lord. But that forgiveness did not remove the sword of the Roman government, nor free him from his cross. That is no argument for death by torture - God forbid! - but it does show that the right of capital punishment is a state affair; the forgiveness of sins in Jesus Christ, an affair of the Church. God rules in both kingdoms, but by diverse means.
A review of AC XXVIII is helpful in sorting it all out: "So it does not interfere with civil government anymore than the art of singing interferes with civil government. For civil government deals with other things than the Gospel does. Civil rulers do not defend minds, but bodies and bodily things against obvious injuries. They restrain people with the sword and physical punishment in order to preserve civil justice and peace. Therefore the Church's authority and the State's authority must not be confused. The Church's authority has its own commission to teach the Gospel and administer the Sacraments. Let it not break into the office of another. Let it not transfer the kingdoms of this world to itself. Let it not abolish the law of civil rulers. Let it not abolish lawful obedience. Let it not interfere with judgments about civil ordinances or contracts. Let it not dictate laws to civil authorites about the form of society."