The hearing was expected to be a perfunctory and procedural exercise, but when Justice Department attorneys asked the court for more time to build their case, the federal judge overseeing the lawsuit fired back.
"When it's a matter of this consequence to this country you roll up your sleeves and get the job done," U.S. Judge Richard Leon said.
Attorneys representing the House condemned the Justice Department for its "attempt to delay" proceedings and notified the court of its intention to file a motion to dismiss the suit by next Tuesday. Justice Department lawyers also said they intend to file a motion to dismiss.
The case is the latest twist in White House efforts to block all former and current administration officials from testifying or otherwise cooperating with the Democrat-led probe.
Kupperman was subpoenaed by House Democrats on Friday. The White House, however, has maintained that Kupperman is entitled to what it calls constitutional immunity, arguing, "Congress may not constitutionally compel the president's senior advisers to testify about their official duties" due to the separation of powers between the executive and legislative branches.
Late Friday, Kupperman's attorney filed a civil suit in federal court in Washington, D.C., asking a judge to sort out the "irreconcilable commands" coming from Congress and the executive branch.
In court on Thursday, attorneys for Kupperman said their client is "in a catch-22."
Kupperman was scheduled to appear for testimony in the House investigation on Monday but did not appear. In a letter to House Democrats, Charles Cooper, Kupperman's attorney, stated that Kupperman would likely not comply with the subpoena until the court had ruled.
Cooper wrote in a letter to lawyers for the House that, if a judge found the House's subpoena to be enforceable, Kupperman would comply with it, and blamed Kupperman's failure to appear on instructions from the president.
"It is not Dr. Kupperman who contests to your client's constitutional claim," Cooper said. "It is President Trump, and every President before him for at least half a century, who have asserted testimonial immunity for their closest advisors."
House Intelligence Committee Chairman Adam Schiff on Monday slammed the White House and Kupperman for his failure to appear, and told reporters that Kupperman could be held in contempt of Congress.
"We will not allow the White House to delay our investigation," Schiff said. "Any acts of obstruction like this, any effort to prevent the Congress and therefore the American people from learning more about the president's misconduct will merely build a public case for obstruction of Congress by this President."
The judge's decision in the case could have a significant impact on whether other executive branch personnel appear before the committee, as the ruling would determine whether arguments of executive branch immunity apply to some other administration officials as well.
The case asks the judge to determine whether the subpoena issued by the House committee is valid under House rules, which, if found invalid, would likely call into question other subpoenas issued to other possible witnesses. It also asks to the judge to consider the president's assertion of immunity over Kupperman's testimony, though the request is specific to Kupperman.
Kupperman's attorney also represents former national security adviser John Bolton, and it's likely that the decision in Kupperman's case would influence whether Bolton would appear before Congress if subpoenaed.
The judge tentatively set a hearing date for Dec. 10.