"For many years, it’s been clear that the detention facility at Guantanamo Bay does not advance our national security -- it undermines it," a newly elected Obama said back in 2010, as he pushed for the prison camp to be closed.
But, despite his promise to close it within a year of being elected, the camp is still fully functional and looks likely to stay that way under the new Trump administration, which has opposed any further releases from Gitmo.
The population has been whittled down from 779 at its top to 55 today but that is still a far cry from the total closure promised.
The trauma left by the 9/11 attacks on the US may be hampering efforts to have the camp closed.
"As much as I might say 'Look, for me the image of Guantanamo is of an unjust system, a violation of international law, a stain on the American record,' it stands as a symbol for others," Scott Lucas, a professor of American history at the UK's Birmingham University, told RFI on Wednesday.
"This is where all the bad guys were put, this is where all the terrorists were put."
Trump has vowed to reverse any closure of Guantanamo Bay and to "load it up with bad dudes".
"Despite the fact that we are 15 years on from 9/11," continues Lucas, "the fact that we still have terrorism around us, even though this is by and large beyond al-Qaeda, as soon as you invoke that word terrorism, you get a rationale that we still supposedly need Guantanamo."
This is an argument that former prisoners object to.
"If Guantanamo was opened because it wanted to protect the world it hasn't done a very good job," says Moazzam Begg, a British-Pakistani binational and former detainee.
"One of the direct consequences of the invasion of Afghanistan and Iraq was the rise of [the Islamic State armed group] Isis and Isis makes al-Qaeda look relatively tame."
Begg was held at Guantanamo Bay for nearly three years on suspicion of being an enemy combatant and fighting for al-Qaeda.
Although he acknowledged having spent time at two non-al Qaeda camps in Afghanistan, he always denied being involved in terrorism.
He was eventually released without charge in 2005 after the British government intervened on his behalf.
Most detainees, though, aren't so lucky.
"From the very start of 2002, what the Bush administration did was, they said these are not prisoners of war, because the US did not recognise al-Qaeda as an entity against which you conduct war," explains Lucas.
"On the other hand, these men [prisoners] were not criminals because terrorism was beyond a law enforcement model and not a matter for police or a standard court system."
Military commissions were brought in to fill the gap.
"They paid far less attention to the evidence brought against these men than a federal court would have," says Lucas.
That meant allowing controversial methods of torture and waterboarding to extract information. In a regular court such methods would never have been allowed.
Campaigners and charities for years have warned that the detention centre was breaching the human rights of terror suspects held for years with no charge.
Many are disappointed to see how the situation has unfolded.
No end in sight
"We really believe that Guantanamo still being open and indefinite detention becoming the law, this is a tragic part of Obama's legacy," Paula Miller of the organisation Witness Against Torture, told RFI.
"We are saddened that Trump wants to keep Guantanamo open and possibly restart a torture programme."
Obama has been scrambling to clear out the prison before he leaves office, amid opposition from Congress, just as President George W Bush tried before him.
Dozens of prisoners inside the facility pose no threat to the US, according to reports, and that has enraged human rights campaigners.
"You either have to return these men to their home countries, and a lot of their home countries don't want them back," Lucas points out. "Let's be honest, some of these men are going to die inside prison."
Fifteen years on, many of them are still not recognised as criminals and never will be.
"You take somebody like Khalid Sheikh Mohamed who's believed to have plotted 9/11, he doesn't get out. He simply perishes there and that's going to be true not only for a high-profile figure like him but some others as well," Lucas says.
Obama leaves office with his promise of closing Guantanamo unfulfilled.
Critics argue that the objective of the prison camp itself, to make the United States a safer place, was also a failure.
"If Guantanamo was opened because it wanted to protect the world it hasn't done a very good job," reckons Begg.
"One of the direct consequences of the invasion of Afghanistan and Iraq was the rise of [the Islamic State armed group] Isis and Isis makes al-Qaeda look relatively tame," he said.