A federal judge was skeptical of the Justice Department's argument Thursday that White House counsel Don McGahn enjoys absolute immunity from congressional testimony.

Judge Ketanji Brown Jackson repeatedly questioned why McGahn should be immune from testifying before the House Judiciary Committee.

Earlier this year, House Democrats subpoenaed McGahn to testify about allegations against President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE, claiming he obstructed former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE from conducting an investigation into Russian interference in the 2016 presidential election.

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The Justice Department on Thursday argued House Democrats had no right to force McGahn to testify and suggested the courts did not have the power to determine which officials were immune from testimony.

The judge, an Obama appointee, fired back, saying she didn't believe the president has the authority to determine immunity.

“That doesn’t seem to me to be in the purview of the executive," Jackson said.

Lawyers for congressional Democrats argued Thursday that McGahn's role in the investigation headed by Mueller into obstruction of justice was "relevant and important to the impeachment inquiry,” though the inquiry primarily focuses on Trump's efforts to persuade Ukraine's president to investigate the Democratic National Committee and former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE, a front-runner in the 2020 Democratic primary.

Democrats also indicated that they wish to question McGahn over Trump's firing of both former national security adviser Michael Flynn and former FBI Director James Comey James Brien ComeySteele Dossier sub-source was subject of FBI counterintelligence probe Judge will not dismiss McCabe's case against DOJ Democrats fear Russia interference could spoil bid to retake Senate MORE.

Jackson said she would deliver a ruling "as quickly as possible,” though further details on the timeframe were unclear.

John Kruzel contributed.

Updated on Friday at 12:26 p.m.