With Democrats not currently planning to vote on a formal resolution authorizing the impeachment inquiry, Pelosi's words could play as mere politics in court.

"Without that vote -- is it an impeachment inquiry?" said Sam Dewey, a Washington lawyer who has served as both House and Senate counsel on Republican-led investigations. "Pelosi can say it, but just because she says it, I'm not sure what that means."

There are five major court cases between the Trump administration and the House that could factor into impeachment proceedings.

In two of the cases, Trump is suing to stop an accounting firm, Mazars USA , and two banks, Deutsche Bank and Capital One, from turning over tax returns and other financial information to various House committees. In another lawsuit, the House Ways and Means Committee wants a judge to force the IRS to give it Trump's tax returns. And in two others, the House is seeking details already gathered by former special counsel Robert Mueller in his criminal probes into obstruction of justice and Russian interference in the 2016 presidential election. The House argues in one of those cases against the administration's assertion of "absolute immunity" for officials protecting former White House counsel Donald McGahn from testifying about what the President directed him to do.

In the coming days, the House could begin touting its new formal impeachment inquiry to the courts. But so far, the House has argued the existence of the inquiry doesn't matter, that it's already in full swing, and that committees are pursuing information about Trump for a number of legislative reasons.

"At least in the immediate future, it's likely more of the two sides staring at each other," former acting House general counsel William Pittard said on Tuesday. Pittard, who led the House legal office under Republican Speaker Paul Ryan, said Pelosi's announcement could greenlight bolder action by committees, ultimately pushing more House subpoena fights to the courts.

One case involving Trump and the House centers around the question of congressional access to grand jury secrets gathered by Mueller. Right now, the House can't see the redacted grand jury details in the Mueller report. But House lawyers argue members need to view the grand jury secrets, in order to consider impeachment. That case sticks out as one where the formality of an impeachment proceeding may matter most.

"For me the million dollar question in this space is if the House is in a formal impeachment proceeding, does it make a court act differently? I don't think we know the answer to that question," said Margaret Taylor, a Lawfare editor and Brookings Institution fellow who previously served as Democratic Chief Counsel for the Senate Foreign Relations Committee.

The Justice Department, in its written argument to keep secret the Mueller grand jury material, pointed to the impeachments of Presidents Bill Clinton and Andrew Johnson, and how those proceedings followed full House votes.

Earlier this month, the Justice Department latched onto the lack of a full House resolution that would govern an impeach inquiry -- and cited a House member's impeachment proposal earlier this year that has so far gone nowhere.

"No court has ever suggested that congressional committees can obtain grand jury material to conduct oversight or consider hypothetical future impeachments based on a lone Representative's referral," the Justice Department wrote in its filing. Judge Beryl Howell, chief of the DC District Court, has yet to weigh in in that case. A hearing with Howell is scheduled for October 8.

In the bank and accounting firm subpoena cases, federal judges so far have agreed that what Congress wants, Congress shall get. In theory, Pelosi announcing a formal impeachment inquiry is just another drop in their bucket of reasons.

"It is simply not fathomable that a Constitution that grants Congress the power to remove a President for reasons including criminal behavior would deny Congress the power to investigate him for unlawful conduct -- past or present -- even without formally opening an impeachment inquiry," Judge Amit Mehta of the DC District Court said in May announcing his decision to allow the House subpoena of Trump's accounting records, including his tax returns.

Trump is appealing Mehta's ruling and another similar ruling by a Manhattan-based federal judge. Decisions from appeals courts could come any day.

Even if it doesn't play into the court fights, the House could gain a slight edge if it were to pass a formal impeachment inquiry. Pelosi's words so far haven't changed procedure. But a resolution, like the ones used in the inquiries of Clinton and President Richard Nixon (Nixon resigned before he could be impeached), gave the Judiciary Committee greater power. In those proceedings, the House gained the ability to subpoena and depose witnesses -- authorities committees already have in everyday business.

The committees don't yet, however, have the power to force witnesses to answer written questions, called interrogatories, former congressional lawyers say. That's another special power the House added by resolution during previous impeachment inquiries.

A few other things could change in the formal impeachment inquiry, according to Dewey.

Barry Berke, a trial lawyer who interrogated former Trump campaign manager Corey Lewandowski last week as a consultant to the Judiciary Committee, could make more appearances as a questioner at hearings. And the Judiciary Committee could step more into the driver's seat in the ongoing court cases -- making appearances or working more closely with the House Ways and Means and other committees.

Even so, House Judiciary Chairman Jerry Nadler already laid down his cards as he questioned Lewandowski a week before Pelosi's announcement: "We amended our rules to empower the chairman to designate specific hearings ... determining whether we should vote articles of impeachment against the President," he said.

"That's exactly what this is."