December will bring a blizzard of action in federal courts that could ultimately settle the limits of congressional power to investigate presidents and compel testimony — and could play a role in the ongoing political drama over impeachment.

In the next two weeks, the Supreme Court and others will handle litigation about congressional subpoenas for White House and national security officials and about lawmakers’ ability to get documents related to President Donald Trump’s finances.

[Trump’s fight against subpoenas reaches Supreme Court]

While Trump’s policies and actions have sparked numerous lawsuits that overlap, the confluence of pending decisions and hearings in the next few weeks could be consequential.

At stake in the judicial branch is not only the scope of House Democrats’ impeachment push, but the constitutional balance between the legislative and executive branches.

Financial records

The Supreme Court is set to determine this month the fate of Trump’s challenge to a House Oversight and Reform Committee subpoena to accounting firm Mazars USA for eight years of his financial and tax records.

Trump’s lawyers have until Thursday to file an appeal, and they are expected to do so. For now, the justices granted Trump’s emergency request to put a hold on a lower court ruling ordering Mazars to comply.

If the justices agree to hear the case, the freeze would remain until they rule, likely before the end of the current court term at the end of June.

But if the Supreme Court declines to hear the case, the House Oversight and Reform Committee could seek the documents as early as this month.

The Supreme Court scheduled a separate but closely related case — Trump’s challenge to a subpoena to Mazars in a Manhattan grand jury probe that is nearly identical to the congressional subpoena — for a closed-door conference on Dec. 13.

The committee has argued that it has legitimate interests in investigating the accuracy of Trump’s financial disclosures and the lease of the Old Post Office Building in Washington as the site of the Trump International Hotel, as well as possible violations of the Emoluments Clause of the Constitution by accepting payments from foreign governments.

More financial records

The second week of December could be called “Emoluments Week.”

The U.S. Court of Appeals for the District of Columbia Circuit will hear arguments Dec. 9 on a lawsuit — filed by more than 200 members of Congress and led by Sen. Richard Blumenthal, D-Conn., and House Judiciary Chairman Jerrold Nadler, D-N.Y. — that alleges Trump violated the emoluments clause.

A three-judge panel will grapple with whether the lawmakers have the legal right to file the lawsuit against the president.

The lawmakers contend that the Constitution requires Trump to obtain congressional consent before accepting benefits from foreign governments, such as those that spend money on events at his hotels or pay rents or fees at Trump’s commercial and residential towers.

And they say Trump “is completely denying members of Congress one of their institutional prerogatives: their right to vote on which, if any, benefits he may accept from foreign states.”

Trump’s lawyers say lawmakers don’t have the right to sue over this. The lawmakers point out that Trump, after awarding the next G-7 summit to his resort in Doral, Florida, reversed course and called it “you people with this phony Emoluments Clause.”

Three days later, on Dec. 12, the full U.S. Court of Appeals for the 4th Circuit in Richmond, Virginia, will hold arguments on a similar emoluments lawsuit brought by local officials in Maryland and Washington. There, too, the issue is whether the officials have a right to file the lawsuit.

Witness testimony

A Dec. 10 hearing centers on a witness at the heart of House Democrats’ impeachment push and whether he must testify before the House Intelligence Committee.

U.S. District Senior Judge Richard J. Leon will hear arguments about a lawsuit from former National Security Council official Charles Kupperman and previously said he planned to rule as soon as late December.

Kupperman filed the lawsuit in October to ask the courts to decide whether he should comply with the subpoena focused on Trump’s dealings with Ukraine or follow a White House directive not to testify.

House lawyers said the Intelligence Committee withdrew that subpoena Nov. 6 and will not reissue it, in part because House Democrats do not want a lengthy court fight to slow their impeachment inquiry.

Both the Justice Department and the House Intelligence Committee told Leon that Kupperman’s lawsuit should now be tossed from court as moot because he faces no consequences for not appearing for the deposition.

Also in December, the House and the Trump administration will be filing briefs in the D.C. Circuit ahead of oral arguments for a House Judiciary Committee subpoena for former White House counsel Don McGahn to testify.

The committee wants the help of the courts to enforce its subpoena of McGahn to testify about what he told investigators in former Special Counsel Robert S. Mueller III’s probe into potential obstruction of justice by Trump.

Some House Democrats consider the McGahn case the key test of congressional subpoena power for other ongoing investigations, although the legal battle might stretch past any impeachment inquiry.

Into the new year

The D.C. Circuit made sure 2020 will start off with just as much action as December. A three-judge panel will hear arguments on the McGahn subpoena Jan. 3.

That’s the same day a separate three-judge panel of the same D.C. Circuit will hear argument about the House Judiciary Committee’s application to receive the usually secret grand jury materials from the Mueller investigation.

Chief Judge Beryl A. Howell of the U.S. District Court for the District of Columbia ordered the Justice Department to give the information to the committee. The Trump administration has appealed.