A federal judge in Washington, D.C., dismissed a lawsuit filed by former Deputy National Security Adviser Charles Kupperman over a subpoena for his testimony in the impeachment inquiry, bringing to a close the one legal fight waged over a subpoena issued as part of the House's Ukraine-focused probe.

U.S. District Judge Richard Leon on Monday granted the House's motion to dismiss the lawsuit, filed by Kupperman's lawyer Charles Cooper, finding that the case is moot after the House withdrew the subpoena for Kupperman's testimony.

"As a result, Kupperman no longer faces the 'irreconcilable commands' of two coordinate branches of government, and he accordingly lacks any personal stake in the outcome of this dispute. Thus, it would appear that this case is moot and should be dismissed," Leon wrote in his opinion.

Kupperman was a deputy to former National Security Adviser John Bolton, who is also represented by Cooper. This lawsuit was thought to be a test run for a potential court fight if Bolton were also to be subpoenaed to testify as part of the impeachment inquiry.

Lawmakers requested that Bolton testify as part of the probe, but did not issue a subpoena to compel his appearance after he didn't show up for the closed-door deposition.

Kupperman and Cooper had argued that the case wasn't moot because the subpoena could be reissued or the House could hold the former White House official in inherent contempt for defying the subpoena, arguments Leon also rejected as "lacking in merit."

The judge pointed to the House attorneys' statements that lawmakers will not reissue the subpoena, writing: "Simply put, I cannot on this record believe there is any reasonable possibility that Kupperman will be re-subpoenaed about impeachment by the House."

And Leon similarly highlighted commitments made by House lawyers that it won't start contempt proceedings against Kupperman in rejecting that argument.

However, Leon wrote that "should the winds of political fortune shift and the House were to reissue a subpoena to Dr. Kupperman, he will face the same conflicting directives that precipitated this suit."

"If so, he will undoubtedly be right back before this Court seeking a solution to a Constitutional dilemma that has long-standing political consequences: balancing Congress's well-established power to investigate with a President's need to have a small group of national security advisors who have some form of immunity from compelled Congressional testimony," the judge wrote.

"Fortunately, however, I need not strike that balance today!" Leon concluded.

House Democrats sought to steer clear of the courts in seeking witnesses and evidence as part of its impeachment inquiry into allegations Trump pushed Ukraine to investigate former Vice President Joe Biden and improperly withheld military aid from the country.

Republicans have argued that the courts were the proper forum to handle disputes over the Trump administration's refusal to comply with congressional subpoenas as part of the impeachment inquiry.

But Democrats claimed that because Trump has exhibited a pattern of attempting to interfere in elections, both in 2016 and now 2020, he is a clear and present danger and must be quickly removed from office.

The House impeached Trump earlier this month, along party lines, for abuse of power and obstruction of Congress. However, Speaker Nancy Pelosi has not yet transmitted the articles to the Senate for trial, as she raises concerns about whether the proceedings will be fair.

She and other Democrats have pointed to Senate Majority Leader Mitch McConnell's comments that he would coordinate an impeachment trial with White House counsel Pat Cipollone as causing major concerns about whether the Senate trial will be fair.

The U.S. Court of Appeals for the D.C. Circuit is set to hear arguments on Friday about whether former White House counsel Donald McGahn can be compelled to comply with a congressional subpoena for his testimony as part of the impeachment proceedings. The House indicated in a filing last week that the testimony could be used as part of the Senate trial, or to determine if additional articles of impeachment are needed.

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