The U.S. Department of Justice has requested a federal judge to overturn a previous ruling that had barred prosecutors from using grand jury subpoenas in an investigation concerning the Federal Reserve's construction cost overruns.

In a court filing on Monday, U.S. Attorney Jeanine Pirro stated that the ruling is no longer necessary, as she has concluded the investigation into the cost overruns and related testimony from Federal Reserve Chairman Jerome Powell.

Pirro terminated the investigation last month, shifting the review of the cost overruns to the Federal Reserve's Inspector General. She did not rule out the possibility of reopening the investigation if the Inspector General uncovers potential criminal misconduct.

On Monday, Pirro asked U.S. District Chief Judge James Boasberg to vacate his earlier ruling, which had dismissed two subpoenas issued by her office during the investigation. She argued that the ruling is now moot since the investigation has ended.

"The U.S. Attorney’s decision to conclude the grand jury investigation raises the question of whether this case has become moot," Pirro wrote. "If a case becomes moot due to the voluntary actions of the party that did not prevail, the court may decline to vacate the ruling."

Pirro, along with other Justice Department officials, has indicated that if the ruling remains in effect, it could undermine a key tool used by prosecutors in the early stages of investigations.

"Should the U.S. Attorney initiate a new grand jury investigation, any future subpoenas would be based on a different record, which is expected to include any information generated by the Inspector General’s analysis," Pirro stated.

Senate leadership has scheduled a full Senate vote on the nomination of Kevin Warsh as Federal Reserve Chairman for the week of May 11. Powell has stated that, due to ongoing legal challenges involving the Federal Reserve, he will remain on the Board of Governors after his term as chairman ends on May 15.