A Washington federal appeals court grappled Friday with the lawfulness of the Trump administration's decision to wind down the Deferred Action for Childhood Arrivals program.

A three-judge panel for the U.S. Court of Appeals for the D.C. Circuit pressed both sides about the September 2017 move to undo the Obama-era policy, which deferred deportation for hundreds of thousands of immigrants who arrived to the United States as children. The panel is considering an appeal of U.S. District Judge John Bates' ruling last year that the reversal was unlawful.

The Trump administration first moved to end the program after then-Attorney General Jeff Sessions in a letter told then-acting Secretary of Homeland Security Elaine Duke that DACA was likely unlawful. Duke, in her own memo, moved to end the program promptly after. Homeland Security Secretary Kirstjen Nielsen, at Bates' direction, later issued a memo. It largely maintained Duke's position but suggested other “sound” policy-related reasons for terminating the program.

Mark Stern, a lawyer for the Justice Department, argued Friday the DACA rescission isn't reviewable by the courts. The decision to undo the program, he said, was an independent exercise of agency discretion made by Department of Homeland Security, and Duke and Nielsen.

The judges appeared skeptical of that argument Friday. Judges Thomas Griffith and Patricia Millett both pressed Stern on whether the agency had genuinely independent reasons to rescind DACA, or if the agency acted on Sessions' view that the policy was unlawful.

“If it's based solely on law, that's going to be reviewable,” Griffith said. “If there are discretionary factors, if there are policy judgments, then that's a different question. To look at the attorney general's letter, that's all based on law. You look at the Duke memo, that's all based on law.”

“We don't start seeing this argument until the Nielsen memo,” the George W. Bush appointee said. “That's frustrating to me, why it would take three bites at the apple before the type of reasoning that we've said for a long time needs to be apparent emerges to the fore.”

Senior Judge Harry Edwards, a Carter appointee, put it more bluntly: “It is very clear that the reason the government chose to act as it did was because as the Attorney General Sessions said, and I think everything following it, what was originally done was unlawful. And you have to justify that because it's a suspect explanation,” he said. “This is a reviewable action.”

The decision to end DACA has sparked several legal challenges. The groups fighting the Trump administration Friday include the NAACP, Princeton University trustees and Microsoft Corp.

A lawyer for the plaintiffs, Jenner & Block partner Lindsay Harrison, also fielded tough questions as she sought to persuade the panel that Nielsen's memo—and the “new rationales” it offered after Bates' April 2018 ruling and remand—were not properly before the court.

Judge Patricia Millett, an Obama appointee, noted that courts remand matters all the time, and agencies are free to add new ideas to their arguments. Millett suggested she didn't see any “untoward appearance” in Nielsen's memo for providing additional explanations for the rescission.

Griffith pressed Harrison about what the plaintiffs' position would be if the court determined there were policy reasons that informed the decision to rescind DACA.

Harrison argued Friday that the additional rationales articulated in Nielsen's memo were infected by legal error. The government's added reasons for rescinding DACA, she later explained, were “bound up” with that legal conclusion.

Griffith raised what he described as another point of “frustration” in the case. President Barack Obama, he said, could not get Congress to grant relief to people who would be DACA recipients, when he decided to announce the program. Trump, he said, had a different view of how to use the executive's discretion on immigration and rescinded DACA.

“Elections have consequences. Courts shouldn't interfere with policy changes. Why isn't that the narrative that explains what's going on here?” the judge asked.

Harrison replied by saying the Trump administration could have taken that approach, but instead chose to “point the finger” at the courts. She asserted again that the government's rationale for undoing DACA, was that the courts tied its hands.

“There's absolutely nothing in the record to suggest the agency actually looked at those considerations, which I think is why the court could hold that it cannot be sure that legal error did not infect the agency's decision,” Harrison later said, in a line of questioning with Millett.

Harrison argued Friday that, ultimately, the DACA rescission was still arbitrary and capricious. She said DHS ignored significant reliance interests when it moved to undo DACA. Hundreds of thousands of people had restructured their lives “on the premise” they'd have deferred status, she said, and the government's memos—including Nielsen's—did little to address those concerns.