The Justice Department won't defend a judge's refusal to toss out the guilty verdict against Joe Arpaio following his pardon by President Donald Trump last year, so a federal appeals court will appoint a special prosecutor to do it instead.

In a 2–1 order Tuesday, the US Court of Appeals for the 9th Circuit found that as Arpaio challenges an order that would keep the guilty verdict against him on the books even after he was pardoned, the court would not get "the benefit of full briefing and argument" unless it brought in a special prosecutor.

Arpaio, the former sheriff of Maricopa County, Arizona, opposed the appointment of a special prosecutor, arguing it would be "totally improper" and that the court would be taking an "accusatory role" by appointing a lawyer to defend the lower court judge's decision. Arpaio is now running for one of Arizona's Senate seats.

Arpaio's attorney Jack Wilenchik told BuzzFeed News that the 9th Circuit's order "raises a lot of disturbing questions about the neutrality of the court." Wilenchik said whether Arpaio would challenge the order would depend, in part, on who the court appointed and what that lawyer was asked to do. If the lawyer was just asked to provide legal analysis and argue, Wilenchik said that would be the "least objectionable" option; if the lawyer were given authority beyond that — the reference to a special "prosecutor" gave him pause, he said — they would have a problem with that.

A judge, in July 2017, found Arpaio guilty of criminal contempt for disobeying an order that his office stop engaging in certain tactics used to catch people suspected of being unlawfully in the United States.

When Trump pardoned Arpaio on Aug. 25, he hadn't yet been sentenced; the hearing was scheduled for October. Arpaio asked US District Judge Susan Bolton in Arizona to vacate the verdict, arguing that because he hadn't been sentenced and there was no final judgment in the case, he had lost the opportunity to appeal and challenge the guilty verdict.

Bolton denied Arpaio's request, writing in her Oct. 19 order that Trump's pardon "does not erase a judgment of conviction, or its underlying legal and factual finding." Arpaio had accepted the pardon after the question of his guilt had been resolved, the judge wrote, even if he hadn't been sentenced yet.

Arpaio appealed. Although the Justice Department had pursued the contempt case, the government's lawyers argued that Bolton should have granted Arpaio's motion to vacate. The Justice Department notified the 9th Circuit in December that it would "represent the government's interests" on appeal but did not intend to defend her order.

Legal advocacy groups filed a friend-of-court brief asking the 9th Circuit to appoint another lawyer to defend Bolton's order, arguing the court should have "the full advantage of the adversarial process" in considering Arpaio's appeal.

The majority of the 9th Circuit panel — Judges A. Wallace Tashima and William Fletcher — agreed, writing that the panel of judges that would ultimately decide Arpaio's case "will not receive the benefit of full briefing and argument unless we appoint a special prosecutor to defend the decision of the district court."

Judge Richard Tallman dissented, writing that the Justice Department had said it would still represent the government's interests, just that it wouldn't defend Bolton's order. The real purpose of the push for a special prosecutor was to challenge Trump's pardon, Tallman wrote, but that issue wasn't before the 9th Circuit. Bolton had acknowledged the pardon was valid and dismissed Arpaio's criminal case, even if she denied his request to vacate the verdict.

"I fear the majority’s decision will be viewed as judicial imprimatur of the special prosecutor to make inappropriate, unrelated, and undoubtedly political attacks on Presidential authority. We should not be wading into that thicket," Tallman wrote. In a footnote, he wrote that the groups advocating for a special prosecutor were not "disinterested" in the outcome, noting that the law firm representing them, Perkins Coie, had represented Hillary Clinton's presidential campaign.

Perkins Coie referred a request for comment to the groups that had argued for a special prosecutor. Justin Florence, legal director of Protect Democracy, one of the groups involved, issued a statement praising the order.

"The DOJ’s abdication of its responsibility cannot take this decision away from the courts and we are glad to see the Ninth Circuit use its authority to appoint a private attorney," Florence said.