An appeals court Monday appointed Christopher Caldwell — a Los Angeles-based lawyer at the private firm Boies, Schiller and Flexner — to serve as a special prosecutor in the ongoing legal fight over whether a contempt of court finding against former Maricopa Sheriff Joe Arpaio should be wiped away due to his pardon by President Trump.

The Justice Department has declined to defend the contempt of court finding, which previously prompted the appeals court panel to vote 2-1 to allow a special prosecutor to defend the contempt finding in briefings and hearings in front of the 9th U.S. Court of Appeals.

The case stems from a successful racial profiling lawsuit Arpaio faced for a 2007 traffic stop, where he wrongfully detained a Mexican man holding a tourist visa. In 2011, a federal judge ordered Arpaio to stop his office’s aggressive tactics of detaining immigrants suspected of being in the country illegally, which is a civil violation. Arpaio was repeatedly found in violation of the court’s order, and after a 2015 civil contempt finding, the matter was referred for a criminal contempt hearing. Trump pardoned Arpaio in August 2017, weeks after he was convicted of criminal contempt of court.

After the pardon, Arpaio requested that the contempt finding against him be voided. A federal judge last October denied the request.