“So what does checks and balances mean?” Jackson, an appointee of President Barack Obama,asked at one point during the court arguments.

James Burnham, arguing for the Justice Department, replied that the dispute between the House Judiciary Committee and McGahn should not be resolved through litigation. He argued that the Constitution and more than two centuries of interactions between the White House and Congress hadn’t required courts to weigh in. And Jackson shouldn’t now, he said.

“So the House can never go to court?” Jackson asked.

“As a general proposition, that’s correct,” replied Burnham, a former White House aide under McGahn who is now serving in a senior position in the Justice Department’s civil division.

Burnham insisted on a broad interpretation of the “absolute immunity” argument the Trump White House has been making in its fight against the House’s various impeachment-related oversight efforts. He said it extended both to former presidents and to top White House aides, whom he called “the alter ego of the president.” Burnham said these aides shouldn’t be forced to answer questions via subpoena because they might reveal information protected under executive privilege.

Facing a barrage of skeptical questions from Jackson, Burnham later conceded, “If you don’t think the president has absolute immunity, that’s a serious problem for my argument.”

Harriet Miers, an ex-White House counsel for President George W. Bush. | Ron Edmonds/AP Photo

The suit, filed by the House Judiciary Committee, centers on McGahn’s role in the White House response to the criminal investigation of alleged collusion between the Trump campaign and Russia.

At Thursday’s hearing, House attorneys insisted that McGahn’s testimony was critical to lawmakers’ efforts to get to the bottom of matters investigated by Mueller, the former special counsel who declined to pass legal judgment on episodes that prosecutors considered potential obstruction of justice.

McGahn showed up hundreds of times in Mueller’s final report, often as the source of vivid recountings of Trump’s attempts to try to stymie an investigation into whether his campaign conspired with Russia on its election-interference attempts.

“The committee needs information from Mr. McGahn, who was a key witness to the allegations of obstruction of justice by the president in the Mueller Report,” House attorney Megan Barbero said. “The committee does require Mr. McGahn to come in and testify so they can have a live witness come in and test his credibility [and] talk to them about the president’s attempts to discredit him and judge for themselves.”

Justice Department attorneys have asserted, as they have under previous administrations, that senior White House advisers like McGahn can essentially ignore subpoenas related to their official duties.

There is no binding legal precedent on the point, but in a dispute a decade ago about President George W. Bush’s firing of U.S. attorneys, a District Court judge rejected the White House’s claims of absolute immunity for one of his White House counsels, Harriet Miers. The case was settled in 2009 and never ruled on by an appeals court.

During discussion of that prior ruling, Jackson seemed to signal that she was inclined to follow that decision unless the Justice Department could find some distinction.

“I am not analyzing this on a blank slate,” Jackson said as Burnham began his argument. “We do have prior precedents from this very jurisdiction. … I’ve been really grappling with this: how today’s case differs from, let’s say, Miers.”

Jackson also expressed discomfort with the Justice Department’s claim that McGahn and other former senior officials were entirely immune from a congressional subpoena, even though many such individuals regularly speak out in public.

“I see all day, many of us do, all kinds of former executive branch officials giving information to the media,” Jackson said. “We understand that people do that even under circumstances in which they could not have done so, perhaps, if they were still in the White House.”

Burnham eventually said he was not arguing that such disclosures are legal, nor ruling out any effort to stop them.

“We have not taken a position on that, Your Honor. I am definitely not disclaiming that,” the Justice Department attorney said.

For their part, the House lawyers urged Jackson to dismiss the Trump administration’s arguments.

“This is what they wish the law were. It’s not what the law is,” said Doug Letter, the House counsel. Later, he added: “At no point in our history have we had absolute immunity.”

While the McGahn case focuses on disclosures in the Mueller report, which was released in April, the resolution of the suit could affect a series of similar standoffs spurred by the current focus of House Democrats’ impeachment efforts: claims that Trump sought to trade U.S. security aid to Ukraine for announcement of an investigation that could embarrass a top Democratic presidential candidate, former Vice President Joe Biden.

One witness sought by the House Intelligence Committee for its Ukraine investigation, former deputy national security adviser Charles Kupperman, filed suit last week asking the courts to tell him whether to comply with the House’s subpoena or to abide by Trump’s direction to ignore it. As the No. 2 man at the National Security Council throughout 2019, Kupperman was a firsthand witness to the pressure campaign on Ukraine.

Kupperman’s suit is before another District Court judge in Washington, Richard Leon, who held the first hearing in that case in a courtroom just down the hall as the arguments before Jackson were playing out. Leon, an appointee of President George W. Bush, is not obliged to follow any decision Jackson issues, but would likely explain any disagreement.

Leon set a hearing in that case for Dec. 10, leaving Kupperman’s subpoena up in the air until the House impeachment hearings are well along or perhaps even complete.

Other Ukraine-related witnesses have also declined to appear and may look to whatever ruling Jackson issues.

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At the close of Thursday’s three-and-a-half-hour hearing, the judge said she was well aware of the interest in her opinion.

“You can rest assured I do understand the significance of all of this. I’ll do my best to turn it around as quickly as possible,” she said, explaining that she was about to embark on a two-week trial that would limit her time.

Jackson added that she’d be open to issuing an oral opinion from the bench, followed by a written decision, if the attorneys asked for an expedited step.

McGahn never testified before the Mueller grand jury, but he still served as a star witness for the special counsel’s investigators. His name is one of the most prominent of any current or former Trump staffer in the final 448-page Mueller report , which recounts episodes when the president might have obstructed justice as he tried to disrupt or outright stop the Russia probe. The information came via five voluntary interviews McGahn did with Mueller staffers, lasting more than 30 hours.

House Democrats have been pressing for McGahn’s testimony dating back to the start of 2019. He was among the more than 80 people and organizations in the president’s orbit who got letters demanding documents from the Judiciary Committee in March. By April, with the Mueller report public, Democrats issued a subpoena for materials from McGahn covering 30 different topics. They also demanded his appearance in May for a public hearing.

Trump’s White House undercut Democrats’ plans to speak with McGahn by requesting a Justice Department legal opinion that found McGahn didn’t need to comply with the subpoena.

White House and Democratic committee attorneys tried to reach a deal over the summer to get McGahn in, but neither side budged. Democrats rejected offers to let McGahn answer questions in writing or sit for a deposition only after getting a peak at what he’d be asked about.

“We believed that the private interview format would satisfy the committee’s stated desire to obtain information from Mr. McGahn,” Michael Purpura, a top White House lawyer, told the court earlier this month in a declaration submitted as part of the case.

Democrats filed their lawsuit seeking enforcement of the McGahn subpoena in August. It was met by motions from McGahn and the Justice Department for an immediate dismissal, saying the courts should stay out of a dispute between the other two branches of government.

“Judicial resolution of disputes directly between the Executive Branch and Congress has been virtually unknown in American history, and is inconsistent with the Constitution’s fundamental principle that the surest safeguard for liberty was to separately equip co-equal Branches with ‘the necessary constitutional means and personal motives to resist encroachments of the other,’” attorneys for the Justice Department and McGahn argued, citing James Madison’s essay No. 51 from the Federalist Papers.