The POTUS has, and I quote, the following:
"The President...shall have Power to grant Reprieves and Pardons for Offences against the United States, except in Cases of Impeachment."
Article II, Section 2, Clause 1
They are detainees of the USA. He has full power to bestow each and every one of them a full unequivocal presidential pardon for all crimes accused and committed against the US. No if's, and's, or but's.