The U.S. Justice Department, silent for months as President Donald Trump's private lawyers have fought to block congressional subpoenas targeting financial information, was invited Monday to tell a Washington federal appeals court what it thinks about the litigation.

The U.S. Court of Appeals for the D.C. Circuit is weighing Trump's challenge to a House Oversight Committee subpoena that was directed to his longtime accounting firm Mazars USA. A three-judge panel on Friday heard from the lawyers in the case for more than two hours, and at times the judges expressed some skepticism at the “stunning” arguments from an attorney for Trump who argued the presidency is largely immune from the broad investigative and oversight authority of Congress.

The panel judges—Patricia Millett, David Tatel and Neomi Rao—on Monday invited the Justice Department to express its views, and the court set a deadline of Aug. 6. Invitations to the Justice Department to participate in federal appeals courts are rare, whereas the U.S. Supreme Court regularly solicit the views of the Justice Department in cases where the government is not a direct party.

Trump is represented in the Mazars case by William Consovoy of the Washington boutique Consovoy McCarthy and Stefan Passantino of Michael Best & Friedrich. Mazars has a team from Blank Rome on its side. The accounting firm has not taken a public position on the subpoena, which was upheld as lawful by a Washington trial judge in May.

The absence of the Justice Department in Trump's subpoena challenge came up during oral arguments last week in the D.C. Circuit. Rao pressed Consovoy about why the Justice Department had not appeared in the dispute. She noted that many of the arguments from Consovoy “relate to the unique constitutional status of the office of the presidency” and the “infringement on his authority.”

“Why is the Justice Department not participating to protect the office of the president, if that's the primary basis of your argument?” Rao asked.

Consovoy said “naturally” the president's personal lawyer would advocate in a case involving Trump's accounting firm. He said he did not know why DOJ was not involved. “I can only speak for my participation and not others,” he said.

William Consovoy William Consovoy of Consovoy McCarthy at a meeting of the Federalist Society. Washington, D.C., April 17, 2018. (Photo: Diego M. Radzinschi/ALM)

A spokesperson from the Justice Department on Monday declined to comment about the D.C. Circuit's invitation to file a friend-of-the-court brief.

The Justice Department also is not a party in the Second Circuit, where Trump's private lawyers are challenging congressional subpoenas targeting Deutsche Bank and Capital One. Lawyers for the two financial institutions—Akin Gump Strauss Hauer & Feld represents the bank, and Murphy & McGonigle represents the credit card company—have not stated any public views on the subpoenas.

The Justice Department's civil division, led by Jody Hunt, is defending Trump and the office of the president in various other lawsuits involving congressional Democrats.

Appellate lawyers in the civil division last week urged the D.C. Circuit to shut down a suit from more than 200 House and Senate Democrats alleging Trump has violated the Constitution's anti-conflicts provisions that limit the president's receipt of gifts and money from domestic and foreign sources.

Separately, the House has sued the Treasury Department and IRS to obtain copies of several years' worth of Trump's tax returns. That case is pending in front of U.S. District Judge Trevor McFadden. The Justice Department is disputing that Congress has any legitimate legislative need to see Trump's tax returns, which he has long vowed to disclose but for a claimed pending IRS audit.