Nov. 1 (UPI) -- As the House authorized the impeachment investigation of President Donald Trump Thursday, federal courts tried determine whether the White House can lawfully block witnesses from testifying as part of the inquiry.
Justice Department attorneys argued in U.S. District Court that House lawmakers cannot force by subpoena any member of the Trump administration, such as former White House counsel Don McGahn, to testify.
Judge Ketanji Brown Jackson's decision will have a significant influence on the impeachment proceedings, as the administration has sought, mostly with success so far, to block government officials from cooperating with the inquiry.
Another legal challenge, involving a lawsuit brought by former deputy national security adviser Charles Kupperman, is asking a federal court to decide whether he should appear for a deposition in Congress, or comply with the administration's demand to ignore the subpoena.
"Kupperman is in a classic catch-22," his attorney, Charles Cooper, said at one of the hearings in Washington, D.C., federal court Thursday. "He cannot satisfy both of them, but he is perfectly prepared to satisfy whichever command this court says is valid."
Judge Richard Leon set a Dec. 10 date for oral arguments in the Kupperman suit, but it's likely House investigators will move to depose him long before that.
Both federal cases are expected to have a tremendous impact on the impeachment landscape, as the White House has moved to block virtually every witness investigators identify for deposition. The Trump administration is arguing, in both cases, that his team has "absolute immunity" with congressional subpoenas.
Democrats argue the government's arguments are groundless, and point to legal precedents that involve the administrations of former Presidents George W. Bush and Barack Obama -- in which federal courts ruled that aides and staffers are required to comply with congressional subpoenas. Those rulings, the Justice Department says, were in error and are not binding for the Trump administration.
Some witnesses, including U.S. Ambassador to the European Union Gordon Sondland, have appeared for depositions only after they were compelled by a subpoena.