"We have people going over, fighting for ISIS and coming back, and we know they are fighting for ISIS, and we take them," he said. "Once you leave this country, you fight for ISIS, you never come back."
Is that really true that they come back and let loose? In a word - no.
New America, a Washington-based think tank, has used public records and news accounts to track Americans who have aided ISIS. According to its analysis, 117 people in the US have attempted to join ISIS or other terrorist groups in Syria, have made it there to fight, or have helped other join these organizations. According to New America's report, 74 of those were arrested before reaching Syria. Forty-three managed to reach that country and join the fight. Of those, 17 were killed and 8 were arrested when they returned home.
"Any American who has traveled to fight with a designated foreign terrorist organization and returned here would be subject to prosecution," said Justice Department spokesman, Marc Ramondi.
One person, Moner Abusalha of Florida, did train with the al-Qaeda affiliated group, the al-Nusra Front, and did return undetected to the US. But rather than stage any attacks on US soil, Abusalha returned to Syria after unsuccessfully trying to recruit more fighters here. He was later killed.
There is no evidence for Trump's claim that US officials have allowed Americans who fought with terrorist groups in Syria to escape punishment when they returned home.