James Emery White writes a succinct summary of what makes war just (according to traditional Christian understandings of the Bible) and how Osama Bin Laden's death fits into that. I encourage you to read the whole post but here's his summary of the conditions for the "Just War" Theory. DRG
Vol. 7, No. 36
When War Is Just
The news spread around the world at the speed of a tweet. Actually, 4,000 tweets per second, according to the site.
Osama bin Laden had been killed.
The response has been interesting: initial jubilation, and then, for many, sobriety. Some were sober because they knew the war on terror would continue, and perhaps for a season, intensify due to retaliations. Others were sober as they wondered whether the entire operation was ethical...
...As a result, the idea of a just war has been with Christian thinking from the beginning. But it has been very carefully spelled out.
Here are the conditions for a war to be just:
*There must be an urgent and imminent threat;
*It must be an act of defense against aggression – never simply for conquest or as an act of aggression – only a defensive war is defensible;
*It must be ordered by one who is in authority to do so;
*It must be for a just cause;
*It must have the right intention – it should not be based on revenge, but as an act of neighbor love and protection, with peace as its goal;
*It should be the last resort; peace and resolution should have been attempted;
*The force used must be proportionate to the desired ends – meaning that the evils caused by the war are less than the evils to be righted;
*It must seek to minimize non-combatant (civilian) casualties;
*It must have a reasonable chance of success.