The U.S. attorney's office appealed a ruling in the Terry Barton case Tuesday.
Attorneys believe the judge is legally required to make Barton pay $14.7 million in restitution.
He ruled against it in June.
Barton's attorney argued the decision is within the judge's discretion.
The court of appeals is expected to make a ruling in several months.
Barton is serving a 12-year sentence for the fire.