With just a year left in his presidency, President Obama is still working to fulfill a major promise from his 2008 campaign: shutttering the Guantanamo Bay prison in Cuba.
Many in Congress oppose closing the prison, so some of his aides and former advisers are urging him to use his executive authority to transfer prisoners to the U.S. for detention or trial. Even with the administration's efforts to transfer prisoners out of Guantanamo Bay, 107 prisoners still remain.
First, the president said, he's going to take one last shot at presenting a plan to Congress to close it.
"I'm not going to automatically assume that Congress says no," he said at his year-end news conference on Friday. "I think it's fair to say that there's going to be significant resistance from some quarters to that. But I think we can make a very strong argument that it doesn't make sense for us to be spending an extra $100 million, $200 million, $300 million, $500 million, a billion dollars, to have a secure setting for 50, 60, 70 people."
Beyond the cost, the president has long argued that the prison fuels the propaganda of terror groups -- "this notion of a gross injustice, that America is not living up to its professed ideals," he said. "We see the Internet traffic. We see how Guantanamo has been used to create this mythology that America is at war with Islam."
But he said he'll wait until Congress has "definitively said no to a well-thought-out plan" before taking steps toward executive action.
Some of his former aides say he already has the authority, should he wish to use it.
Gregory Craig, the White House counsel in 2009 and Cliff Sloan, the special envoy for Guantanamo Closure in 2013 and 2014, argued in an op-ed last month that Article II of the Constitution gives the president the exclusive authority to determine the facilities in which detainees of the U.S. military are held.
The framers of the Constitution gave Congress the power to declare war, while explicitly disallowing them from making war. Combined with Article II of the Constitution, it makes the president commander-in-chief of the military. This role, Craig and Sloan argue, gives the president the authority to make tactical military decisions. Under this reasoning, while Congress can authorize detentions and military tribunals, it cannot conduct military campaigns, and it cannot dictate where detainees are held and tried.
Last month, Congress passed a $607 billion defense policy bill that bars the president from transferring any of the remaining detainees to the U.S. Mr. Obama signed the bill, but he included a signing statement warning that, "Under certain circumstances, the provisions in this bill concerning detainee transfers would violate constitutional separation of powers principles."
His former aides went further, writing that Congress' ban on using funds to transfer detainees is "plainly unconstitutional" because it "prevents the president from discharging his constitutionally assigned function of making tactical military decisions," they wrote.
Other scholars argue that violating the congressional ban would be unconstitutional, and if Mr. Obama were to act unilaterally to close Guantanamo, it would be the kind of action that he criticized then-President George W. Bush for taking.
"I don't see him having unilateral power unless there's an emergency situation," Chris Edelson, an American University professor who studies the Constitution and the presidency, told CBS News. "It's a dangerous argument they're making that essentially depends on the president having the ability to set aside" Congress' intentions.
Mr. Bush drew criticism for ignoring Congress at times. When Congress passed the 2005 Detainee Treatment Act that explicitly prohibited torture or cruel, inhuman or degrading treatment of prisoners in the wake of the Abu Ghraib scandal, Mr. Bush included a signing statement that said his administration would only carry out the law "in a manner consistent with the constitutional authority of the President."
As a candidate in 2007, Mr. Obama pledged to stop undermining the Constitution and Americans' freedom in prosecuting the war on terror.
"No more ignoring the law when it is inconvenient. That is not who we are," he said at the Woodrow Wilson International Center in August 2007.
But it's not just the legal challenges that make it difficult to close Guantnamo Bay. Edelson said the current political climate makes it harder for Mr. Obama to argue that bringing more terror suspects into the U.S. is a good idea, even if they will be transferred into the highest-security prisons.
"After Paris and San Bernardino, people are afraid, and there's a lot of politicians I think who are going to exploit that," he said.
CBS News Senior National Security Analyst Juan Zarate agrees that the current threat environment makes the argument a difficult one, but said there are other practical realities to keep in mind, too.
Closing Guantanamo "without a real plan for how the United States plans to maintain custody in perpetuity of dangerous terrorists who will not face trial of any sort, and [without] plans to capture, interrogate, and detain terrorists in the future is a prescription for disaster," Zarate said. "If the President proceeds alone without answering the hard questions, he risks handing his successor a major mess on the national security front," he said.