"He's always supported the idea that you should be able to nevertheless detain people indefinitely as combatants, " said Padmanabhan, now a professor at Vanderbilt Law School.

NPR: Gitmo Closure Elusive, Obama Looks At Other Steps

Vijay Padmanabhan, who was a State Department lawyer responsible for Guantanamo-related cases in the Bush administration, said Obama faces three major questions to achieve his goal of shutting Guantanamo.

NPR: Gitmo Closure Elusive, Obama Looks At Other Steps

Padmanabhan said Obama needs to figure out what level of risk he's willing to accept in Yemen, come up with a strategy for prosecuting detainees and determine how to handle those who are considered dangerous but for whom there isn't sufficient evidence for prosecution.

NPR: Gitmo Closure Elusive, Obama Looks At Other Steps