As President Trump zoomed past a lowly personal milestone — his 10,000th false or misleading statement in his 27-month-old presidency, according to The Post Fact Checker — he let fly a series of whoppers on a subject that logic would suggest he’d be better off leaving unremarked: family separation. The president, whose own administration imposed and then rescinded a systematic policy of wrenching migrant children from their parents, with no protocol in place to reunite them, now poses as a paragon of compassion that ended cruel laws in place before he took office. This is false.

During an interview with Fox News on Sunday, Mr. Trump suggested that his heartless policy had continued practices in place under the Barack Obama and George W. Bush administrations, among others. In contrast to his predecessors, Mr. Trump said, “we’ve been on a humane basis . . . we go out and stop the separations,” he said. “The problem is you have 10 times as many people coming up with their families. It’s like Disneyland now.”

In fact, the “zero tolerance” policy was formulated (with White House approval) by Mr. Trump’s then- attorney general, Jeff Sessions. The policy mandated automatic imprisonment […]