House Democrats and former deputy national security adviser Charles Kupperman separately asked a federal judge on Monday to block President Trump's acting chief of staff from intervening in a lawsuit over subpoenas related to the House's impeachment inquiry.
Trump's top aide, Mick Mulvaney, had filed a motion in D.C. District Court on Friday seeking to join Kupperman's lawsuit over a subpoena in order to fight the House Intelligence Committee's efforts to compel his own testimony.
But Democrats argued that the original lawsuit is moot since they withdrew the subpoena directing Kupperman to testify.
Kupperman also filed a brief on Monday opposing Mulvaney's motion arguing that he should be directed to file a separate lawsuit.
The Democrats wrote in their filing that even if the case was not moot at this point, Mulvaney and Kupperman are in very different circumstances.
"While Kupperman seeks a declaration from this Court as to whether he should comply with his subpoena or follow the President’s directive, Mulvaney seeks only a declaration that the House Defendants cannot compel him to comply with his subpoena or take any action against him if he does not," they wrote. "Unlike Kupperman, Mulvaney does not state that he would comply with his subpoena if this Court rejects the claimed absolute immunity."
Despite filing a lawsuit, Kupperman has stayed neutral in the fight between the president and the House. He argued in his complaint that he was seeking a court ruling to decide which of the two "irreconcilable commands" he was facing — the congressional subpoena and the White House's directive not to cooperate — have legal authority.
Mulvaney, meanwhile, is asking the court to block the subpoena he received last week. If Mulvaney's motion prevails, it would throw him into a lawsuit in which his own boss is a named defendant.
Kupperman also argued in his filing that Mulvaney may have jeopardized his ability to claim immunity from the House's efforts to subpoena him when he essentially said in a press conference last month that the White House was seeking an investigation from Ukraine into former Vice President Joe BidenJoe BidenManchin to vote to nix Biden's vaccine mandate for larger businesses Congress averts shutdown after vaccine mandate fight Senate cuts deal to clear government funding bill MORE in exchange for congressionally approved security funding.
"Mulvaney has publicly discussed the events at issue in the House’s impeachment inquiry, including appearing to admit that there was a quid pro quo relationship between the President’s decision to withhold appropriated financial assistance from Ukraine and a Ukrainian investigation into what happened to a Democratic server in 2016 (an admission he subsequently sought to disavow)," Kupperman's filing reads. "Plaintiff, in contrast, has never publicly disclosed information relating to any of his official duties, including the matters under investigation by the House."
Mulvaney later walked back his comments.
The House Democrats pursuing the impeachment investigation, who are embroiled in a mounting number of legal fights with the Trump White House, have made clear that they are not willing to fight for Kupperman's testimony in court.
Kupperman and his former boss, John BoltonJohn BoltonWhen will Biden declare America's 'One China, One Taiwan' policy? India's S-400 missile system problem Overnight Defense & National Security — GOP unhappy with Afghan vetting MORE, share an attorney, who wrote to House Democrats last week hoping to tantalize them with the promise of new details about the White House's efforts in Ukraine if they are willing to compel the former national security adviser's testimony.
Judge Richard Leon, a George W. Bush appointee, will preside over a phone conference with the two sides later on Monday afternoon.