Federal courts have so far been asked to weigh in on relatively few standoffs central to the Ukraine-focused impeachment inquiry. That could change, depending on the Democrats' boldness and how encouraged they feel following the routing of Trump's legal arguments.
Federal judges throughout history haven't often come down on protecting the President from investigation. Instead, they have in several situations delivered to prosecutors and the impeachment investigators in the House the materials they seek -- sometimes exceptionally fast.
Trump so far has done his best to delay new information from getting into the House's hands.
His White House counsel wrote to House leadership early last week to say it wouldn't cooperate in the impeachment inquiry. The letter invoked the Constitution and due process for the President. The dissenting judge on the Circuit's tax return case, Trump-appointee Neomi Rao, appeared to endorse many of the White House's arguments.
In past impeachment proceedings, the courts have undermined the President's wishes. During Whitewater, President Bill Clinton was forced by a unanimous Supreme Court to testify under oath in a civil lawsuit, which led to his impeachment for lying and obstruction. During Watergate, President Richard Nixon faced multiple fast-moving court cases that ultimately forced details to Congress and prosecutors that prompted his resignation before the full House voted on articles of impeachment.
Howell also bluntly told the Justice Department's legal team she would need to back the House in its needs during a formal impeachment proceeding.
"By my reading of the Supreme Court and D.C. Circuit law, I owe enormous deference, if not absolute deference, when it comes to the exercise of the impeachment power to how the House decides to conduct itself," Howell said Tuesday.
Michael Gerhardt, a CNN analyst and University of North Carolina law professor, pointed to moments in the Howell hearing as an example of how far Trump's legal team has swerved from history. The "argument shows not just how aggressive the President is being, but how much disdain they have for settled law. Most judges would just recoil at that," Gerhardt said.
The Circuit Court, in its tax returns decision Friday, appeared to signal as much. They discussed in the majority opinion how four decades of Presidents previously had disclosed their tax returns, and Congress would be well within its rights to ask for the tax returns or make law forcing presidents to disclose them.
"Congress can require the President to make reasonable financial disclosures," the court wrote.
That language could weigh against Trump in another ongoing case where he is trying to stop Congress from requesting his New York tax returns under a new state law. Judge Carl Nichols, the most recent Trump appointee, has not made any major decisions yet.
The Circuit's opinion is likely to embolden Democrats. Before House Speaker Nancy Pelosi announced the impeachment inquiry involving Ukraine, she emphasized the Democrats' strategy involved the courts as the committees investigated several allegations against the President.
"We are taking the work of the Committees into the courts," Pelosi said at a September 12 news conference.
Since launching the impeachment inquiry last month, Pelosi has described White House defiance of the investigation as an abuse of power and "further evidence of obstruction."
There's some possibility that if Democrats turn to the courts for more help in the Ukraine investigation, it could be a risky strategy, Gerhardt said.
"The courts are likely to not want to get involved in this" unless prompted, according to the legal scholar. And while lower-court judges will likely stick to historical decisions that hurt Presidents under investigation, Gerhardt added, it's possible the US Supreme Court could be more sympathetic to Trump's legal arguments.
Rao's dissent, in particular, could be a preview of the thinking of some Supreme Court justices. She notes the question of whether the House can subpoena the President's tax returns for a possible legislative reason "has never been squarely addressed by the Supreme Court."
Rao points out that Congress has not yet authorized an impeachment inquiry, meaning, to her, it's abusing its legislative power with the tax returns subpoena. The lack of a formal resolution authorizing the impeachment proceeding is a point White House counsel Pat Cipollone also raised.
"Allowing the Committee to issue this subpoena for legislative purposes would turn Congress into a roving inquisition over a co-equal branch of government," Rao wrote.
The writing has been on the wall since spring that Trump would have difficulty blocking House subpoenas. Two trial level judges had made it clear: Congress gets what it says it needs.
"To be sure, there are limits on Congress's investigative authority. But those limits do not substantially constrain Congress," Judge Amit Mehta of the DC District Court wrote in May, deciding that the House Oversight Committee could obtain Trump's records from his accounting firm. (The ruling Friday from the DC Circuit, again siding with the House, was the appeal to this decision, and upheld Mehta's ruling.)
"This court is not prepared to roll back the tide of history," Mehta added, referring to the Nixon-era congressional investigative steps that led to the Watergate impeachment hearings as well as requests Congress made during Whitewater before opening the official impeachment proceeding against Clinton.
Mehta ruled less than a month after receiving the case about Trump's accounting records, which amounts to lightning speed for a sometimes-circumspect court.
Judge Edgardo Ramos in the Southern District of New York made a similar decision to Mehta's on a case about a subpoena for Trump's bank records from Deutsche Bank and Capital One, taking only 23 days to rule.
Trump is still awaiting a decision from the 2nd Circuit Court of Appeals, which is reviewing the case that was before Ramos. Both Deutsche Bank and Capital One have said they wouldn't have Trump's tax returns to give to the House under that subpoena. Yet the House still could get still-private financial details about Trump if it ultimately wins the case.
Not all judges have been as firmly against Trump. Some of the cases between Trump and the House have landed in the hands of this President's appointees, including at the DC District Court, which has four new judges. So far, those judges have moved more slowly in taking up questions related to Congress. One three-month-old case, for instance, before Judge Trevor McFadden, over a House subpoena of the IRS for Trump's tax returns, declined to expedite the case, and won't have a hearing until early November.
Yet much depends on the draw (the process that randomly assigns a judge to a case). In yet another case, between the House and Trump regarding forcing former White House counsel Don McGahn to testify, attorneys for the House sought Howell as the adjudicator. When she said there was no good reason she should have the case, the court spun its wheel and reassigned the matter to Judge Ketanji Brown Jackson, an Obama appointee.
Jackson is set to hear arguments over the McGahn subpoena in the House probe of whether Trump obstructed justice on Halloween.
Even outside the House versus Trump proceedings, federal judges in lower courts came down harshly against the President last week.
On Friday alone, four federal courts rejected the President's immigration policies. One judge ruled against the President's emergency declaration to build a border wall, while three others tore apart the administration's rule that would make it more difficult for immigrants who rely on public assistance to get green cards or visas.
And on Monday, Judge Victor Marrero of the federal court in Manhattan ruled against Trump two and a half weeks after getting a case regarding a subpoena of Trump's tax returns.
The trial-level judge decided Trump couldn't block the state prosecutor from obtaining his tax returns. The ruling sits outside of the fights between the President and Congress, yet Marrero worked into his 75-page opinion ways to slash at the protections Trump had asserted -- and his administration's legal approach entirely. This was not a court sympathetic to the White House in an inter-branch fight.
Marrero, in his opinion, called assertions that Trump is above the law while he serves as President "repugnant to the nation's governmental structure and constitutional values."
Trump is, again, appealing.
CNN's Jeremy Herb contributed to this report.