It was once among the simplest ways to boost a diesel truck’s power, performance, and reliability: pay a local shop to discreetly remove its emissions controls using an illegal “defeat device.”
Now the federal government has largely ceased prosecuting those who sell and install such devices.
These devices, which often combine hardware and software, surged in popularity around two decades ago as increasingly cleaner tailpipe systems placed greater strain on engines. Some truck owners and mechanics have viewed defeat devices as essential.
By 2020, the most recent data available, the EPA estimated that emissions controls had been removed from over 550,000 diesel pickups in the preceding decade, representing roughly 15 percent of all diesel trucks originally certified with those controls. The agency calculated that this equated to adding more than nine million additional diesel pickups to U.S. roads, emitting nitrogen oxides at levels up to 300 times the legal limit.
Following a high‑profile 2015 case in which Volkswagen was discovered to have secretly employed defeat‑device software in millions of vehicles, the Justice Department began pursuing criminal charges under the Clean Air Act against shop owners who installed the devices on individual vehicles. Those prosecutions have now been discontinued, according to a Department of Justice post on X earlier this year that received little attention outside the trucking community.
The policy shift aligns with the Trump administration’s extensive rollbacks of clean‑air regulations, which it characterized as costly and burdensome. The White House and the EPA have targeted greenhouse‑gas rules and sought to roll back Biden‑era incentives for electric vehicles in favor of fossil‑fuel‑powered alternatives. The agency has also moved to weaken California’s stricter auto‑emissions standards and delay upcoming tailpipe regulations.
In the X post, the department explained that it was “exercising its enforcement discretion” to cease pursuing criminal charges. It affirmed its commitment to “sound enforcement principles, efficient use of government resources, and avoiding over‑criminalization of federal environmental law.”
While the department said it would continue to pursue civil enforcement — suing violators — for misconduct, it declined to comment for this article.
Because the change rests on prosecutorial discretion, the policy could be reinstated under a future administration.
The new policy has already prompted prosecutors to dismiss pending cases that could have resulted in years of imprisonment. The impact has been especially severe for defendants whose cases were already closed, some of whom are now seeking presidential pardons or attempting to recover legal expenses.
Mackenzie Spurlock, 31, owns Matanuska Diesel, a small shop in Wasilla, Alaska, that was raided by EPA investigators in 2022. He was charged with collecting at least $30,000 for removing emissions controls from at least 20 vehicles.
He pleaded guilty last year, which now makes him a felon — a status that, among other things, bars him from rejoining the National Guard, where he served six years as an aircraft mechanic. “After going through this experience, it makes you realize how weaponized the government was at that point,” Mr. Spurlock said. He was sentenced to probation and a $32,000 fine.
Spurlock argued that modern emissions‑control systems often render trucks inoperable in Alaska’s harsh winters, leaving drivers stranded in subzero temperatures. He said he was simply trying to help his customers.
Emissions‑control systems incorporate hardware in the exhaust that is linked to a vehicle’s computer and uses a combination of methods to trap and neutralize pollutants. However, they can also reduce engine power and fuel efficiency. If a vehicle’s computer detects a failure in the emissions system, it can place the truck in “limp mode,” rendering it inoperable until repairs are made.
“Nobody wants to harm the environment,” Spurlock said. “It isn’t about trying to break the law. People want reliability.”
The EPA has taken steps to address automatic engine shutdowns related to onboard diagnostics that affect truckers and farmers who rely on diesel vehicles. The agency referred questions about the criminal‑policy shift to the Justice Department.
Stewart Cables, an attorney in Boulder, Colorado, who specializes in defeat‑device cases, said that he and other defense lawyers have long argued that the Clean Air Act authorizes only civil actions — not criminal prosecutions — for vehicle emissions. Historically, the government pursued civil enforcement until 2018.
“It was always our argument that, ‘Ok, this is illegal, but it’s a civil violation,’” Cables said. “Then they started charging felonies, which turned everything upside down.” Cables is now seeking a pardon for Spurlock in light of the Justice Department’s new policy on criminal prosecutions.
According to Elizabeth Loeb, a former Justice Department lawyer who worked on defeat‑device cases during the first Trump administration, such devices became widely available around 2016. The kits, often comprising both hardware and software, could be found easily online.
“You could search ‘delete pipes’ on Amazon or eBay and hundreds of results would appear,” Loeb said.
The Justice Department sued eBay in 2023 over the sale of defeat devices and other potentially harmful products. A judge dismissed the case, ruling that eBay could not be held liable for its users’ products. Amazon now prohibits the sale of devices that may interfere with an engine’s emissions‑control system.
Federal officials gained expertise in defeat devices during the massive 2015 case against Volkswagen. VW had programmed cars to detect laboratory testing conditions and temporarily activate emissions controls during those tests, but to disable them on real‑world roads, resulting in nitrogen‑oxide emissions far exceeding legal limits.
Volkswagen ultimately paid more than $30 billion in fines and legal fees. Other automakers faced similar accusations; for example, Mercedes‑Benz agreed last year to pay up to $150 million in a settlement with nearly all U.S. states regarding the devices, while denying wrongdoing.
Amid the scandal, U.S. prosecutors turned their attention to smaller operations that sold or installed defeat devices.
The pace of criminal charges accelerated dramatically during the Biden years. Prosecutors filed charges in a handful of cases before the 2021 inauguration and brought about 40 cases throughout the Biden administration.
In 2020, the EPA issued an “enforcement alert” warning that shops could face criminal liability for installing defeat devices and reminded the public of the severe health impacts of air pollution. Nitrogen oxides contribute to smog and respiratory illness, while diesel trucks also emit high levels of particulate matter, soot, lead, and mercury.
Vanessa Waldref, a former U.S. attorney for the Eastern District of Washington who oversaw several defeat‑device investigations, said the department’s reversal on criminal enforcement was disappointing. Her team had been confident in the legal basis of the cases and had devoted substantial resources to the investigations.
“Criminal enforcement is a critically important tool for sending an unequivocal message of accountability and for establishing community standards to protect public health and the environment,” Waldref said, now a partner at the firm Singleton Schreiber focused on environmental matters and wildfires. She also contested the Justice Department’s claim that vehicle‑related air‑pollution cases should be limited to civil penalties, arguing that such penalties can become “just the cost of doing business.”
Lawyers such as Stewart argue that the Clean Air Act permits criminal liability for tampering with emissions controls only at stationary sources like power plants or refineries. “We believe the Trump administration was correct in eliminating criminal liability for this conduct,” Stewart said. “If you want to make tampering with a mobile source a felony, go to Congress.”
