President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE on Thursday moved to dismiss a lawsuit filed by an aide to former national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE who was seeking a ruling on whether he must comply with a congressional subpoena to testify in the House impeachment inquiry.

The filing to the U.S. District Court in Washington, D.C., cited Trump's official capacity as president. In it, he sought to have a judge dismiss White House official Dr. Charles Kupperman's lawsuit seeking guidance on whether he should comply with the subpoena or the president's directive not to cooperate.

A representative for Trump argued that the president's direction should supersede any prospective court ruling.

"Although Dr. Kupperman claims that he needs this Court’s guidance as to whether he should comply with the House’s attempt to subpoena his testimony, he already knows the answer," the filing states. "He should follow the directive of his former employer (the President) to not testify pursuant to the President’s invocation of Dr. Kupperman’s absolute immunity from testimonial compulsion.”

The filing argues that the "proper course" would be for Kupperman to abide by Trump's insistence that his administration not cooperate with the impeachment process rather than whatever a judge ultimately determines.

It also cites that the former aide should not comply because he dealt with matters pertaining to the president and worked in close proximity to him.

The filing lays out some of Kupperman's roles on the national security council. It noted that he was present in meetings with Trump and on calls with heads of state, that he advised or prepared advice for the president, that he communicated the president's decisions to others in the executive branch and that his title denoted him as one of Trump's most senior aides.

“Leaving the President’s senior most aides open to compelled congressional testimony would allow Congress to encroach upon the independence and autonomy of the Presidency... to reveal the President’s thinking or influence his decision-making on sensitive or controversial matters," the filing states.

House Democrats are pursuing an impeachment inquiry into whether Trump abused his office by pressuring the Ukrainian government to investigate a domestic political rival.

Several current and former administration officials have given private testimony to lawmakers in the investigation after being subpoenaed to do so. The first two witnesses to testify publicly on Wednesday did so under subpoena.

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While Republicans have argued none of the witnesses have first-hand information about alleged wrongdoing, the White House has blocked most of those who would have first-hand information from testifying. Kupperman would represent a witness with more direct access to the president.

But Kupperman filed a lawsuit seeking a resolution on whether to comply with the subpoena or with the president's instructions. House Democrats withdrew the subpoena last week in an acknowledgement that Kupperman's lawsuit could lead to a drawn out process.

An attorney representing both Kupperman and Bolton said this week that the two men would be willing to testify if the courts rule that they should comply with the congressional subpoena.

In a curious move, lawyers for acting White House chief of staff Mick Mulvaney Mick MulvaneyOn The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security Blockchain trade group names Mick Mulvaney to board Mick Mulvaney to start hedge fund MORE indicated he would join Kupperman’s lawsuit last week. Mulvaney was subpoenaed for testimony but has not complied.

On Tuesday, Mulvaney reversed course and said he would not seek to join Kupperman's lawsuit and would instead follow Trump's instructions to ignore the subpoena.

Updated at 10:48 p.m.