Image: Kirstjen Nielsen
U.S. Secretary of Homeland Security Kirstjen Nielsen speaks on migrant children being separated from parents at the southern border during a White House daily news briefing at the James Brady Press Briefing Room of the White House in Washington on June 18, 2018.Alex Wong / Getty Images

At a White House briefing Monday, Nielsen defended the Trump administration’s newly enforced “zero tolerance” policy for people trying to cross into the U.S. from Mexico without visas. Nielsen falsely claimed that federal law requires family separation when parents, even those legally seeking asylum, are held for prosecution. And she said family separation is not a new policy.

So far this spring more than 2,300 child migrants have been separated from parents — many fleeing violence in Central America —…