Charles Kupperman, a former top national security official, originally filed the lawsuit asking the court for clarity on whether he had a constitutional duty to testify after conflicting statements from House Democrats and the White House.
The White House ordered Kupperman not to cooperate with a subpoena from House Democrats. He declined to appear before the House committees leading an impeachment inquiry into Trump last month.
Since then, Trump’s former national security adviser, John Bolton, with similar conflicting orders, joined the same lawsuit, refusing to participate in the impeachment inquiry until the legal dispute was settled.
“Mr. Mulvaney, like Mr. Kupperman, finds himself caught in the division, trapped between the commands of two of its co-equal branches … with one of those branches threatening him with contempt,” Mulvaney’s attorneys, Christopher Muha and William Pittard, wrote in the filing.
House lawyers withdrew Kupperman’s subpoena earlier in the week, saying they would be guided by similar litigation’s outcome regarding the subpoena of former White House counsel Donald McGahn.
Mulvaney’s attorneys added he should be able to join the suit not only because he faced similar conflicting orders, but also because, unlike Kupperman, Mulaney was still an active member of the administration.
“Mr. Mulvaney is both a closer and more senior adviser to the President than was Mr. Kupperman, the filing said. “In short, there are reasons unique to Mr. Mulvaney’s position that might form the basis of a judicial ruling against the House Defendants’ threatened actions, reasons that Mr. Kupperman necessarily cannot advance.”
House intelligence committee Chairman Adam Schiff, D-Calif, leading the inquiry, is named in the suit along with several top House Democrats and Trump.
White House counsel Pat Cipollone instructed Mulvaney not to testify Friday, saying he was protected by “constitutional immunity” for Trump’s current and former senior advisers.
The filing comes on the heels of National Security Council official Lt. Col. Alexander Vindman accusing Mulvaney in testimony released Friday of helping to coordinate a quid pro quo in which the administration offered a meeting with Ukrainian President Volodymyr and Trump in an effort to pressure Kiev to investigate Democratic presidential candidate Joe Biden and his son, Hunter Biden.
In a news conference last month, Mulvaney admitted there was a quid pro quo, but shortly after clarified and denied the remarks.
On Friday, Rep. Jim Jordan, R-Ohio, got a seat on the House intelligence committee for the public phase of the impeachment inquiry, replacing Rep. Rick Crawford, who is retiring at the end of his term.
Jordan was part of a failed effort last month to censure Schiff over his recounting of Trump’s controversial July 25 call with Zelensky leading. A partial transcript of the call has been made public in light of the whistle-blower complaint that lead to the impeachment inquiry.