I'm pretty sure there was a plan at the beginning of all this to hold a sort of Nuremburg trial for all of the captured terrorists. I'm also pretty sure that whole plan fell apart either shortly before or shortly after we invaded Iraq and there was no actual plan B.
You can say what you want to about the value of the lives of terrible people like KSM, but it has been two decades. $#!+ or get off the pot. There's no earthly reason other than government incompetence keeping these animals alive and detained at US tax dollar expense for that long.
Shoot them, set them free, or (my preference) find a middle ground and set them free over the Atlantic at 20,000 feet, halfway back to their homeland.
Too many zeros. 200 feet. I can live with the rest of that.