WASHINGTON – President Trump sought to stanch a public outcry over his administration’s “zero tolerance” immigration policy Wednesday, signing an executive order to end family separations at the U.S.-Mexico border after days of insisting he was legally unable to act. Trump’s abrupt reversal, contradicting his own aides’ defense of the practice, signaled a political retreat after an international backlash over images of hundreds of children being taken from their parents and held in cage-like detention facilities. But it remained highly uncertain whether the president’s hastily drafted order to keep families together in federal custody while awaiting prosecution for illegal border crossings would withstand potential legal challenges.