The Diesel Brothers of reality TV fame are appealing a federal court judgment that penalized them for $848,000 in Clean Air Act violations.

The Woods Cross-based pickup truck modifiers are extending a four-year legal battle on to the 10th U.S. Circuit Court of Appeals in Denver, where their attorney says they have a better shot of prevailing.

In early March, U.S. District Judge Robert Shelby of Salt Lake City ruled the Diesel Brothers committed about 400 violations of pollution law for installing and selling emission control defeat devices.

The decision was a victory for Utah Physicians for a Healthy Environment, which sparked the litigation in 2016 with a letter to the defendants alleging violations after seeing smoke-spewing trucks on the TV show.

The environmental group later sued under provisions of the Clean Air Act that allow citizens to seek civil damages against violators.

But Cole Cannon, the Diesel Brothers’ attorney, said Monday they see a different legal landscape in the circuit courts.

“We believe there is a circuit split in law regarding the ability of private parties to bring cases under the (Clean Air Act),” Cannon said in a written response to a request for comment about the appeal.

“Notably the 4th and 9th circuits have different standards of review, and it is our opinion the 10th circuit has not yet ruled on this issue,” Cannon said.

Different rulings on a similar issue in the circuit courts are one of the factors the U.S. Supreme Court considers in deciding whether to hear a case.

“We think it’s in the general public’s interest to get clarity on the point, and certainly in our clients’ best interest to find out,” Cannon said.

Defendants are David “Heavy D” Sparks, several Diesel Brothers companies he owns, and two others on the TV show, Joshua “Redbeard” Stuart and Keaton “The Muscle” Hoskins.

On the Discovery Channel show, now in its sixth season, the Diesel Brothers modify vehicles and give away customized diesel trucks in sweepstakes.

Shelby also issued a permanent injunction barring the Diesel Brothers from further violations, which he said stemmed from unlawful operations that still are economically enriching the defendants.

Those benefits continue, Shelby said, “extending well beyond the profits from these prohibited activities to defendants’ status as television and social media celebrities, the reputation and notoriety of their brands, and the economic leverage they have used to accumulate assets and start new businesses.”

Most of the $848,000 must be paid to the U.S. Treasury. But Shelby further ruled that $90,000 will go to the Davis County Tampered Diesel Truck Restoration Program.

The judge said the doctors’ group demonstrated that the Diesel Brothers caused irreparable injury by increasing the amounts of toxic pollutants breathed by Northern Utahns and that monetary damages can’t compensate for injuries suffered.

Seven Utah counties repeatedly have not met federal air pollution standards, especially on the Wasatch Front. The doctors’ groups says ozone and fine-particulate pollution emitted by diesel engines cause various health problems, including cancer.

But the Diesel Brothers contended that most of the trucks with defeat devices ended up going to sweepstakes winners out of state. Shelby discounted that argument, saying it did not matter where in the United States the trucks are causing pollution.

The Diesel Brothers filed a notice of appeal with the circuit court on April 7. As of Monday, the court had not set a date for a hearing.

Reed Zars, representing the doctors’ group, did not immediately respond to a request for comment about the appeal.