To handle the mounting workload, the House’s general counsel, Douglas Letter, a former Justice Department litigator, and his staff of seven lawyers have increasingly relied on volunteer lawyers at white-shoe law firms and at public interest groups — including several prominent veterans of the Obama legal team — to help research and draft court filings.
Representative Adam B. Schiff, Democrat of California and the chairman of the Intelligence Committee, which was a party in one of the subpoena lawsuits for Mr. Trump’s banking records, portrayed the increasing litigation as an unfortunate necessity.
“The blanket refusal to comply with any legitimate process has forced us to go to court to validate Congress’s power of oversight,” he said. “If we don’t, we are at risk of losing that power, and that would be a tragedy for the country because it would take any limit off the executive.”
Republicans say it is the Democrats who are out of control and violating traditional norms of governance. The Justice Department has accused the House of asking the judiciary “to take its side in political disputes” and of trying to “use federal courts to accomplish through litigation what it cannot achieve using the tools the Constitution gives to Congress.”
For most of American history, Mr. Tiefer said, Congress never went to court over disputes with the executive branch. The seeds of change began during the Watergate scandal, when Congress enacted a special law enabling a Senate committee to sue President Richard M. Nixon to try to gain access to his Oval Office tapes.
In the post-Watergate reform era, the House created a small general counsel office, raising the possibility of filing civil lawsuits seeking enforcement of its subpoenas to executive branch officials if a president tried to block them. But that threat remained essentially theoretical for more than a generation, as the two branches resolved such disputes through negotiations.
But in 2008, House Democrats went to court to compel disclosure of information from the Bush administration about its firing of a group of United States attorneys. In 2012, House Republicans sued for internal Obama Justice Department documents related to the botched gun-trafficking case known as Operation Fast and Furious.