This weekend, David Greggory of Meet The Press suggested in a discussion that this phrase implied that KSM would be tried and executed no matter what the Trial results would be.
When Flight control originally used the phrase, I am sure they had no idea what the final outcome would be as the ground teams scrambled to create a way to clean the remaining supply only using the limited equipment that was available in the orbiter. The Phrase "Failure is Not an Option" is only about the absolute commitment the team would consider when trying to save the lives of the men on Apollo 13.
Holder was not suggesting that KSM would not be provided a fair trial, but only that as his team works for that conviction, to fail would put to risk a greater population of US citizens. With so much at stake,.. I would hope the Attorney General will not consider failing.