A federal appeals court in Washington hears oral arguments Tuesday in a clash between the House and the Trump administration that threatens to inexorably tip the historical balance of government power away from Congress and to the president.

At the heart of the House lawsuits are Trump moves to brush aside Congress in two of its long-held areas of power and put the onus on lawmakers to try to stop him. President Donald Trump has gotten his way for more than a year, thanks in part to the House’s reliance on a court system that crawls compared to the speed of today’s politics.

One case involves Trump’s fight-all-the-subpoenas stonewalling of the House impeachment inquiry in early 2019, focused on the House Judiciary Committee’s demand for testimony from former White House Counsel Don McGahn. The committee issued the subpoena more than a year ago to McGahn to testify about events described in the special counsel probe into Trump’s possible criminal obstruction of justice.

The other is Trump’s February 2019 move to spend money on border wall construction, even when Congress didn’t give in to his appropriations demands for the project in a clash that resulted in the longest government shutdown in history. Last week, the administration launched a website to provide an update on construction along the U.S.-Mexico border.

But the legal showdown is about more than Trump’s actions, said former Maryland Democratic Rep. Donna Edwards, who helped gather a bipartisan group of 78 former members of Congress to sign a brief supporting the House in the cases.

“This is really a very egregious abuse of his authority and really stepping over the constitutional lines. But what about the next president, and what gets ignored then?” Edwards told CQ Roll Call.

Without the power to compel information from the executive branch to review how it spends the money that Congress appropriates, Congress can’t do its job for the American people, Edwards said, “and this framework that’s been set up for these 200-plus odd years is a framework that is in danger of falling apart.”

House lawyers will defend that framework Tuesday before the full U.S. Court of Appeals for the District of Columbia Circuit, in a telephone hearing that will be streamed live over the internet.

The nine judges who will decide the cases — seven of whom were appointed by Democratic presidents — will wrestle with a more fundamental legal question. At issue is whether the Democratic-led House even has the legal right to use the federal courts to enforce committee subpoenas or stop unlawful spending of appropriations.

The Justice Department will argue that courts should stay out of it, because allowing the House to go to courts over “informational disputes” would also cause a shift in constitutional power, from the president to Congress. And that decision also would politicize the judicial branch because judges will appear to take sides in partisan fights, the Trump administration says.

Those familiar with congressional oversight have given the D.C. Circuit doom-filled forecasts about what would happen if they rule that courts must stay out of such political disputes.

The House Judiciary Committee told the D.C. Circuit that if courts don’t get involved in such disputes between the two political branches, it would “effectively eliminate Congressional oversight as we know it.” A group of legal scholars told the D.C. Circuit that Congress “is impotent without the power to secure documents and witnesses.”

And that bipartisan group of former members of Congress told the judges that “it is hard to overstate the consequences of congressional inability to obtain information from the Executive Branch” — only that it would open a “Pandora’s box” and be a “seismic shift” that signals the end of Congress’s long-held powers of inquiry.

Former North Carolina Democratic Rep. Brad Miller, who signed that brief, said such a ruling would mean that the president can control information regarding the day-to-day operation of government so that it never gets to voters.

“And controlling information is just incompatible with a democracy,” Miller said.

Former House general counsels who served under both Republican and Democratic control of the chamber pointed out in a brief that the McGahn case is only the fourth interbranch subpoena dispute in court since Watergate.

That’s largely because the House had the perceived ability to enforce subpoenas in court, the former general counsels said, as demonstrated in the dispute involving the Senate Special Whitewater Committee into President Bill Clinton. When the White House refused to comply with the committee’s subpoena for the notes of a meeting with the Clintons’ personal lawyers, the Senate voted to authorize its legal counsel to go to court to enforce the subpoena.

“The very next day, the White House agreed to release the disputed notes,” the general counsels said in the brief. “No lawsuit was ever filed; the mere knowledge that one would be was enough to resolve the dispute.”

The House arguments in the border wall and McGahn cases have met resistance so far. U.S. District Judge Trevor N. McFadden, a Trump appointee, ruled that courts were not the place to settle the border wall dispute over congressional appropriations power.

While U.S. District Judge Ketanji Brown Jackson, appointed by President Barack Obama, ruled that McGahn must testify, that decision was overturned by a three-judge panel of the D.C. Circuit, and a George W. Bush appointee and a Trump appointee comprised the majority.

That three-judge panel suggested Congress has other political tools such as impeachment or withholding appropriations that it can use to coerce the executive branch into complying with subpoenas. The House says those weapons are far too blunt.

The full D.C. Circuit vacated that panel ruling so it could decide both the cases, which set up Tuesday’s arguments.

But the arguments won’t be the end of the story. The D.C. Circuit will rule at a later date, and both sides are poised to press their side to the Supreme Court.

Some House Democrats point to the McGahn case as the test case for enforcing more subpoenas in their oversight investigations into the Trump administration.

They might have to look at any victory in institutional terms, since Trump might have already won in one sense. The legal fight appears likely to drag on past the November presidential election.