Washington (CNN) Former White House counsel Don McGahn is appealing Monday night's ruling that he must testify to House impeachment investigators.

McGahn and the Justice Department also asked DC District Judge Ketanji Brown Jackson to say that he not be forced to testify while the appeal plays out.

The ruling, and how an appeals court interprets it, could have major implications for several aspects of the ongoing congressional impeachment probe into President Donald Trump, from the inquiry into a quid pro quo with Ukraine to questions about whether Trump lied to or attempted to obstruct special counsel Robert Mueller.

It also may lead to a major judicial ruling on where the White House can draw the line to protect its confidentiality in separation of powers disputes.

The moves in court, coming 14 hours after Jackson's decisive decision in favor of House Democrats, show that the Trump administration will fight aggressively to hold off McGahn's testimony -- and potentially others' whom they are blocking from the impeachment inquiry.

Jackson's searing 120-page opinion Monday said McGahn must testify and disagreed with the executive branch's legal claims of current and former officials having "absolute immunity."

The McGahn case has been seized upon by House lawyers and the President as a harbinger of other clashes with the House over witness testimony and White House immunity.

The President tweeted about the ruling Tuesday morning, saying the media is "reading far too much into" it. "I am fighting for future Presidents and the Office of the President. Other than that, I would actually like people to testify," Trump wrote

The D.C. Wolves and Fake News Media are reading far too much into people being forced by Courts to testify before Congress. I am fighting for future Presidents and the Office of the President. Other than that, I would actually like people to testify. Don McGahn's respected.... — Donald J. Trump (@realDonaldTrump) November 26, 2019

Trump mentioned McGahn as well as others the House has unsuccessfully pursued , including former national security adviser John Bolton, Secretary of State Mike Pompeo, outgoing Energy Secretary Rick Perry and acting chief of staff Mick Mulvaney.

Even if Jackson refuses to pause McGahn's testimony, the House has agreed to give the administration a seven-day delay so it could appeal the ruling to the US Court of Appeals for the District of Columbia Circuit.

McGahn has a "significant chance" of winning on appeal, the Justice Department writes, adding that no appeals court has settled whether the executive branch can stop White House officials from testifying in congressional proceedings or whether the House can enforce its subpoenas of administration officials in court.

Other potential witnesses

A delay for McGahn's case would bring a minor sigh of relief to other House impeachment witnesses who have rested on the White House's immunity from testimony, which is backed up by Justice Department policy.

So far, top former national security officials John Bolton and Charles Kupperman, acting chief of staff Mick Mulvaney , and national security council lawyers John Eisenberg and Michael Ellis have all used the same legal reasoning as McGahn not to speak about the President and Ukraine.

Among that group, only Kupperman has gone to court. So far, the former deputy national security adviser says he knows significant information about Trump's approach but asked a judge to decide whether he must appear before Congress. That case continues on separately from McGahn, and won't be decided until at least mid-December or January.

The case, in some ways, could be a test of the heightened secrecy of national security discussions in the White House.

Charles Cooper, lawyer for Kupperman and Bolton, said Kupperman's lawsuit would continue despite the ruling against McGahn.

Cooper notes that the House legal challenge in the McGahn case did not involve national security issues, making Kupperman and McGahn quite different in how protected they could be by the administration.

"(A)ny passing references in the McGahn decision to Presidential communications concerning national security matters are not authoritative on the validity of testimonial immunity for close White House advisors, like Dr. Kupperman, whose responsibilities are focused exclusively on providing information and advice to the President on national security," Cooper said in a statement Tuesday.

But Jackson wrote in her opinion Monday that the White House's immunity claims had so little grounding in law, it wouldn't make a difference if the aides had dealt with national security.

How McGahn fits into impeachment

The House has wanted McGahn's testimony since April -- when Mueller released his final report, but the Justice Department argues that more delay won't hurt.

The interplay between McGahn, other White House witnesses and a fight over Mueller's grand jury material has been like a game of musical chairs with no judicial end in sight.

The committee argues McGahn would be a significant witness on whether the President attempted to obstruct the Russia investigation, since he spoke to prosecutors and the FBI several times about Trump's direction to fire Mueller. The committee says McGahn may also be able to weigh in on whether Trump lied to Mueller in his written answers -- a suggestion that caught the House's attention after Trump's interest in leaks that could hurt the Democrats in 2016 arose during Roger Stone's recent criminal trial.

The House Judiciary Committee's obstruction of justice and Russia-related investigation is separate from the Ukraine quid pro quo inquiry, which is nearing its end as the House prepares articles of impeachment against Trump, possibly including obstruction of justice.

So far, the House has avoided using the courts during its Ukraine-related inquiry.

Instead, it has focused its legal efforts on the McGahn case and a case seeking access to grand jury secrets from the Mueller probe.

The DC Circuit is scheduled to hear arguments about the Mueller grand jury secrets in early January. So far, the House has won, with a district court judge saying it should get what it needs to investigate the President.

The House previously argued it won't be able to effectively question McGahn without the grand jury information about Trump and his campaign, the Justice Department argued. McGahn served as the campaign's legal counsel and in the White House until October 2018. Therefore, the Justice Deparment says the courts should McGahn case should wait until the grand jury case is resolved.

UPDATE: This story has been updated with additional information about the case and impeachment investigation.