A protest against the Trump administration’s family-separation policy in Washington last June. (Evelyn Hockstein/For The Washington Post)

LAWYERS FOR the Trump administration object to the suggestion that officials have a moral and humanitarian duty to track children and reunify them with their parents after they have been separated by the government. Sure, said Justice Department attorneys in federal court the other day, hundreds and possibly thousands more migrant children remain split from their parents than previously acknowledged. But it really would be a headache to patch up families torn apart by the administration’s war on immigrants.

That’s a paraphrase, but not by much. Requiring the government to determine the number and whereabouts of migrant babies, toddlers and teens wrenched from their parents during a nine-month span when family separations were carried out covertly would “blow the case into some other galaxy of a task.” So said Justice Department lawyer Scott Stewart, who pleaded the administration’s case.

Fortunately, U.S. District Judge Dana M. Sabraw, who has overseen the lawsuit seeking to reunify migrant families, is clear-eyed on the issue facing him. “It’s important to recognize we are talking about human beings,” the judge said Thursday. “Every person needs to be accounted for.”

The matter of separated children has arisen again because of a lie of omission on the administration’s part. After a national furor last spring, President Trump canceled the “zero tolerance” policy under which more than 2,700 children were removed from their parents in a six-week span ending in June. Mr. Sabraw, ruling in a lawsuit brought by the American Civil Liberties Union, ordered those children reunified with their parents.

What went unmentioned at the time was that Border Patrol agents had been routinely splitting up families beginning in July 2017, nine months before the “zero tolerance” policy was announced. Incredibly, no one kept count of how many children had been taken away during that period, or systematically tracked where and with whom they ended up. Last month, a report by the Department of Health and Human Services inspector general concluded that thousands of children had been confiscated from their parents in those nine months.

With the exception of relatively few officials, no one knew. So when Mr. Sabraw issued his reunification ruling last June, his order covered only those families torn asunder during the six weeks in which the separations were public. Now the ACLU is asking the judge to include the previously split children.

The government argues speciously that the first group of children constitute a completely different case. In fact, the only distinction is between the administration’s covert and overt cruelty. The U.S. government cannot be permitted to leave migrant children indefinitely orphaned on the grounds that reunifying them with parents would be a pain in the neck.