Oral arguments are set to take place this week, when U.S. District Court Judge Emmet Sullivan will have to explain why he has not signed off on the Justice Department’s motion to dismiss its case against former National Security Adviser Michael Flynn.

The hearing marks another extraordinary turn in an extraordinary -- and seemingly interminable -- case that has brought pressure upon both the Justice Department and the judge overseeing it. After calling into question the DOJ’s choice to drop Flynn’s prosecution, Sullivan is now in the position of defending his own decision.

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“It is unusual for a criminal defendant to claim innocence and move to withdraw his guilty plea after repeatedly swearing under oath that he committed the crime,” Sullivan argued in a court filing, referring to Flynn's past guilty plea of lying to investigators. “It is unprecedented for an Acting U.S. Attorney to contradict the solemn representations that career prosecutors made time and again, and undermine the district court’s legal and factual findings, in moving on his own to dismiss the charge years after two different federal judges accepted the defendant’s plea.”

The D.C. Circuit Court of Appeals got involved in the matter when Flynn requested what's known as a writ of mandamus -- in this case, an order from a higher court to a lower court or official to fulfill their duties -- to force Sullivan to toss the case.

Sullivan, instead of signing off on the DOJ’s motion to dismiss, had called on third parties to submit amicus curiae (“friend of the court”) briefs arguing against the government’s move to drop a case where the defendant had previously pleaded guilty.

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Sullivan, who has yet to make a determination on the matter, bristled at the call for a writ of mandamus -- calling it inappropriate at this stage because there remains the possibility he could still dismiss the case on his own.

Sullivan himself has now obtained legal counsel. His attorney is Beth Wilkinson, who represented Supreme Court Associate Justice Brett Kavanaugh during his contentious Senate confirmation process. Fox News reached out to Wilkinson, who declined to comment on the matter.

Rule 48(a) of the Federal Rules of Criminal Procedure states that prosecutors “may, with leave of court, dismiss an indictment, information, or complaint.” Retired Judge John Gleeson, chosen by Sullivan to file an amicus curiae brief, claimed in a May Washington Post op-ed he co-authored that this means a motion to dismiss “is actually just a request.” As a judge in 2013, however, he wrote that courts are “generally required to grant a prosecutor’s Rule 48(a) motion unless dismissal is ‘clearly contrary to manifest public interest.’”

Trump allies have criticized Sullivan's handling of what was initially thought to be the coda of Flynn's legal saga.

"What I see is the Federal Rules of Criminal Procedure don’t allow for what Judge Sullivan is doing," former Acting Attorney General Matt Whitaker told Fox News in May. Whitaker said that prosecutors are the ones who decide which cases they pursue, and that "there’s really no discretion on the judge based on the current state of the law."

The DOJ’s motion to dismiss came after unsealed documents revealed FBI notes pertaining to their interview of Flynn in January 2017 conducted as part of the Russia investigation. Those notes showed that there had been discussion over whether the goal of the interview was to find out the truth or to get Flynn to lie so he could be prosecuted or fired.

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Trump indeed fired Flynn for lying about his contacts with the Russian ambassador, but after the FBI notes were made public the president expressed regret given the information that has since come out. Trump had previously said he was “strongly considering” offering Flynn a pardon.

Arguments will take place before a D.C. Circuit Court panel composed of Judges Neomi Rao, Karen L. Henderson, and Robert L. Wilkins. Rao was appointed by Trump, Henderson by President George H.W. Bush, and Wilkins by President Barack Obama.

Sullivan himself was first appointed to be a judge on the D.C. Superior Court by President Ronald Reagan, and was tapped to join the federal bench by President Bill Clinton.

In 2009, Judge Sullivan presided over the case of former Sen. Ted Stevens, R-Alaska, who had been found guilty of lying on a Senate ethics form before a whistleblower in the FBI revealed that evidence had been withheld from Stevens.

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In that matter, Sullivan tossed the verdict after what Stevens called "prosecutorial misconduct."

Sullivan told prosecutors on the case that he'd "never seen such mishandling or misconduct."

Fox News' Tyler Olson contributed to this report.