A group of two-dozen former federal judges on Friday defended Judge Emmet Sullivan's refusal to immediately approve the Justice Department's bid to drop the prosecution of Michael Flynn, stepping into a politically fraught case that has raised fresh questions about the extent of the judiciary's authority over criminal prosecutions.

In a 24-page friend-of-the-court brief, the former judges asserted Sullivan has full authority to review the government's effort to abandon the prosecution of Flynn, who has twice admitted to lying to federal investigators about his past discussions with the Russian ambassador to the United States.

Judges are not "mere scriveners of whatever dismissal the government places before them," the former judges said in their brief, filed by lawyers from San Francisco-based Keker, Van Nest & Peters.

Earlier this month, Sullivan appointed a former federal judge to oppose the abandonment of the prosecution and address whether he should consider holding Flynn in contempt for perjury. Flynn's lawyers filed a challenge in the U.S. Court of Appeals for the D.C. Circuit. The case has teed up questions about the power of judges presiding over criminal prosecutions.

Sullivan, represented by veteran trial attorney Beth Wilkinson, is set to respond by Monday to Flynn's petition in the appeals court. Other amicus briefs, including one signed by former D.C. Circuit Judge Kenneth Starr, have been filed in support of Flynn.

The former judges behind Friday's brief had been appointed by Democratic and Republican presidents, and they said they "represented centuries of judicial experience and have presided over thousands of criminal cases." The signatories included Nancy Gertner, a Harvard Law School professor and former federal judge in Massachusetts, along with former Manhattan federal judge Shira Scheindlin and Howard Matz, who served as a federal trial judge in Los Angeles from 1998 until 2011.

In their brief, the former judges defended Sullivan's inquiry into the Justice Department's abrupt abandonment of the case, more than two years after Flynn initially pleaded guilty and agreed to cooperate with the special counsel investigation into Russian interference in the 2016 election. Flynn subsequently fired his lawyers at Covington & Burling, and his new legal team has spent months arguing that Flynn should be allowed to walk away from his guilty plea.

The Justice Department based the decision to dump the case on its newfound belief that the FBI lacked a valid investigative reason for conducting the January 2017 interview at the core of Flynn's prosecution, but the move has been widely disparaged as a politically motivated favor for a Trump ally. It came only months after the Justice Department leadership intervened in the case of Roger Stone, overruling career prosecutors to suggest a shorter prison term for the president's longtime friend and confidant.

On Friday, the former judges questioned whether the Justice Department had acted in "bad faith" in moving to drop Flynn's case and argued that Sullivan has more than a mere "ministerial" role in responding to that sudden step.

"In an effort to explain its dramatic change in position, the government has raised, and petitioner reiterates, serious questions about prosecutorial bad faith. Those questions should be addressed by the district court in the first instance," the judges wrote.

The judges also defended Sullivan's appointment of Debevoise & Plimpton partner John Gleeson, a former federal judge in Brooklyn, to oppose the Justice Department's motion to dismiss.

"Furthermore, because of the government's change of heart, there is an unusual lack of adversity here," they wrote, adding that Gleeson's appointment was appropriate "to fill the gap left by the government's abandonment of its former position."

To some observers, Sullivan is fully embracing his power as a member of a co-equal branch of federal government to weigh cases in his court. Others have argued that Sullivan overstepped his authority when he refused to quickly dismiss the Flynn case at the request of Attorney General William Barr and Timothy Shea, who until earlier this month was serving as the top federal prosecutor in Washington. Barr has called the Flynn prosecution an "injustice."

"The judge has already abused his wide discretion by inviting outside advocates to weigh in, which would make a circus of the solemn judicial proceeding," wrote J. Michael Luttig, a former judge on the U.S. Court of Appeals for the Fourth Circuit, in a Washington Post op-ed published Monday. Luttig said the D.C. Circuit should not order Sullivan to dismiss the Flynn charges but instead send the case back to a different judge for further review.

Earlier this week, 16 former members of the Watergate special prosecution task force filed their own brief in the D.C. Circuit, urging the panel to reject Flynn's appeal and allow Sullivan's consideration of the case to proceed.

Those former prosecutors—represented by Zuckerman Spaeder partner William Taylor and Lawrence Robbins, a partner at Robbins, Russell, Englert, Orseck, Untereiner & Sauber—said Sullivan has merely been following the court's requirement to "exercise independent judgment when deciding a motion to dismiss federal charges."