MY COMMENT:
The mainstream media never told you that of the nearly 800 detainees who passed through (41 remain) the US military detention facility at Guantanamo Bay, Cuba, tens of thousands were never sent there. In fact, 731 have been RELEASED from Gitmo. NONE have been executed, blown up, hacked to death, dragged naked and lifeless through the streets, drowned or burned alive, all things our enemies have done to us and/or our allies. But I digress.
Tens of thousands of detainees captured and then released during the early parts of the Global War on Terror (which still rages on) were never sent to Gitmo because they were not deemed high value detainees. A high value detainee potentially has valuable information that could save many lives, like the 41 detainees still held at Gitmo.
What President Trump's words tell us is that none of the detainees in Syria require any further interviewing. It tells us that these jihadi's are no longer a threat to the United States nor do they posses any valuable information.
Having at least dual citizenship with some European countries, President Trump feels, and rightly so in my opinion, that these detainees should be retained by their countries of national origin. This is the law.
When captured on the battlefield, the status of the detainee establishes whether or not they are a POW, protected person, civilian, or an unlawful combatant. At the end of hostilities, all detainees may be released to their country of national origin. All the players know this.
The exception may include those accused of war crimes. Even so, the controlling authority may release the detainee to their country of origin as long as there is no known threat to that person's safety. As far as I know, none of the European countries in question have threatened to kill their countrymen upon their return, they just don't want them.
Maybe if we labeled them "refugees" Europe would take them back?