Now don't get me wrong, there were definitely different tribes who did have certain representatives in place. However, the government was very much a monarchy, where the Monarch led through the representative of men like Moses, Joshua, and so on.
The Lord leads the Israelites and establishes their system of government through the works of Moses. (Indeed if you ever truly want to know how a government should be structured, I think you should probably follow God's model here.)
But the key point is that the Lord was leading the Israelites along the way. He established the death penalty clearly at this time, and He administered it with perfect grace. We see this most clearly with the death of Achan after he stole from the Lord Himself.
So then how could I say that I was against the death penalty with this in mind? Clearly I don't think I'm better than God.
Indeed I don't. No man is going to execute such perfect judgment. That is actually the exact reason that I am against the death penalty in our world today.
As I made the distinction earlier, God was the leader of the ancient Israelite government, and when he decides who should live and die, he does do so perfectly.
Today, we have no government that is directly led by God. Yes, I know that God is sovereign in all he does, but if we use that excuse here, we might as well stop worrying about anything we do because God is in control of everything.
At the end of the day, I agree with the idea of a death penalty in principle (an eye for an eye), but I do not trust the human errors that come with a government administered by men. Death is a very permanent state that no man can undo. It seems too much for me to trust a justice system administered by men in such a crucial area.
Indeed our current system admits the possibility of mistake. There are massive initiatives put in place to allow for an appeals process, once again administered by men, to sift through and ensure there are no innocent people who die.
This appeals process probably catches most mistakes, but it too will not be perfect. Yes, I doubt that the United States has put to death too many people who are innocent, but even one would be too many.
Also, who are we men to decide that certain crimes are worthy of death anyway? We're not God. We don't make those types of decisions. Or we don't until we come together and form governments.
In conclusion, I leave you with the words of Gandalf the White,
"Deserves it! I daresay he does. Many that live deserve death. And some that die deserve life. Can you give it to them? Then do not be too eager to deal out death in judgement. For even the very wise cannot see all ends."
Except of course the Lord. he does see all ends, and everything entirely, and that omniscience and sovereignty is exactly why we should leave the decision of who lives and who dies up to him.