Because both the US and international law provides for the use of the Death Penalty. A trial was carried out, and he was found guilty. He now gets to appeal. If the appeals don't work, he'll face whatever punishment the court deems fit, and the court, like various US trials before it, has deemed the punishment to be death. And like the Nuremburg trials of the 1940s, it has deemed that death to be carried out by way of hanging.Just Bush being self righteous really. But as the occupier (Iraq for lack of better term is an occupied country, rather than an independent nation) we have the right to see that Saddam's rights are carried out. We wanted Iraq to emulate our version of democracy, so why does he have to face such a "cruel" death as capital punishment (its in the constitution "cruel and unusual punishment"). Tangents aren't just a math term.
This is how we roll for those guilty of crimes against humanity.