Ripping the emissions system out of a diesel truck used to be the kind of decision that ended with a federal indictment, not just a check-engine light. For most of the last decade, the Department of Justice treated aftermarket defeat devices as a criminal enterprise worth prosecuting, not a civil paperwork problem. That posture didn’t survive 2026. Between a Justice Department memo killing pending prosecutions, two rounds of presidential pardons, and an EPA proposal that would swap hard engine derates for a dashboard warning light, the federal government spent the first seven months of this year quietly dismantling the enforcement machine it had spent a decade building.
The Memo That Ended the Prosecutions
On January 21, 2026, Deputy Attorney General Todd Blanche signed an order directing federal prosecutors nationwide to drop every pending criminal case built on Clean Air Act defeat-device tampering charges and to stop opening new ones. Blanche framed the move as necessary for even-handed prosecution and better use of department resources, but the legal reasoning behind it was new and, by the Justice Department’s own internal admission, contested. The theory holds that the onboard diagnostic software regulating a truck’s emissions system isn’t technically something manufacturers are required to maintain under the statute, meaning tampering with it can only be punished as a civil violation, not a felony. EPA’s own career attorneys wrote an internal memo disagreeing with that reading, arguing Congress intended emissions compliance to last for a vehicle’s full working life, not just at the point of sale. The Ninth Circuit hadn’t even ruled on the theory, which originated in the appeal of an autobody shop owner’s conviction, before Blanche applied it nationwide. The order affected more than a dozen active prosecutions and over twenty open investigations, including a case against a father-and-son diesel parts business in Washington state.
Around the same time, EPA’s own enforcement arm fell in line. Jeffrey Hall, confirmed in December to lead the agency’s Office of Enforcement and Compliance Assurance, told staff he had directed EPA investigators to stop pursuing criminal referrals for onboard diagnostic tampering entirely, after speaking directly with the Justice Department about how to align the two agencies’ approach.
Pardons Stacked on Top of Dropped Charges
Dropping future and pending cases didn’t touch the people already convicted, so the White House handled that separately. In November 2025, President Trump pardoned Troy Lake, a Wyoming diesel mechanic who had served seven months in federal prison for conspiring to disable emissions controls on diesel trucks, after Wyoming Senator Cynthia Lummis lobbied for his release and described the case as an example of politically motivated overreach by the prior administration. Then on July 3, 2026, Trump announced pardons for six people he said had been wrongfully prosecuted simply for fixing their own vehicles, calling the prosecutions an act of weaponization and stupidity. The White House later confirmed five additional pardons issued that same day, at least three of them tied to similar Clean Air Act pollution convictions, bringing the day’s total to eleven. Defense attorneys and a White House official identified the recipients to news outlets as Ryan and Wade Lalone, Matt Geouge, Tim Clancy, Mac Spurlock, Joshua Davis, Barry Pierce, Aaron Rudolf, Adam Kidan, Jack Harvard, and Jonathan Achtemeier. Trump posted about the move himself, writing, “I AM SETTING THEM ALL FREE, RIGHT NOW!”
A pardon erases a criminal conviction, not the underlying violation. It doesn’t undo an EPA civil penalty, and it doesn’t retroactively make a defeat device legal to sell going forward, since the Clean Air Act’s tampering ban is still on the books, unchanged by anything DOJ or the White House did this year. What changed is enforcement discretion and executive clemency, both of which a future administration, or a Ninth Circuit ruling rejecting Blanche’s civil-only theory, could reverse just as quickly as they appeared.
The industry DOJ spent a decade chasing wasn’t small. A 2020 EPA study found that emissions controls had been removed from roughly 550,000 diesel pickups over the prior decade, adding an estimated 570,000 tons of excess nitrogen oxide to the air, pollution linked to respiratory illness and premature death. Civil settlements over that period ranged from painful to historic: a Nashville parts distributor paid $320,000 in 2024 for selling illegal defeat devices, while Volkswagen’s 2017 guilty plea over its own factory-installed defeat devices carried a $2.8 billion criminal fine on top of $1.5 billion in separate civil resolutions. Next to Volkswagen’s math, the aftermarket delete business was a cottage industry, but the legal exposure facing individual mechanics and shop owners was, until this year, existential.
Where EPA’s Own Rule Fits In
The DOJ memo and the pardons dealt with the people already caught. EPA’s proposal, announced July 9 and open for a 45-day public comment period, addresses the underlying complaint that fed the delete market in the first place: false fault codes. Selective catalytic reduction systems dose diesel exhaust fluid into the exhaust stream to convert NOx into nitrogen and water vapor, and when a sensor detects a problem with that dosing, the engine computer has historically responded by cutting engine speed or power outright, sometimes over sensor errors rather than genuine failures, particularly in cold weather. EPA’s proposal would swap that automatic derate for an audible or visual alert on new model year 2027 highway engines and vehicles, and the agency says it is weighing a separate guidance process that would let manufacturers apply the same fix to trucks already on the road. Backfire broke down the compliance side of that proposal, including the warranty and useful-life provisions bundled into the same rulemaking, in a separate deep dive.
That’s a meaningfully different thing than a defeat device, and the distinction is worth being precise about. A delete kit or a tuned-out sensor stops the SCR system from dosing DEF at all, which is exactly what drives up NOx emissions. EPA’s proposed fix keeps the dosing system doing its job; it only changes what happens when a sensor throws an error, trading a roadside limp-mode for a warning light. The practical effect for an owner-operator is similar to what the delete crowd wanted all along, a truck that doesn’t strand itself over a fault code, but the difference matters: one path required breaking federal law, and the other is being built into next year’s trucks with EPA’s own signature on it.
What This Actually Means If You Own a Diesel
None of this makes deleting a diesel a good idea, legally or mechanically. DOJ’s enforcement pause rests on a legal theory the Ninth Circuit hasn’t ruled on and EPA’s own lawyers dispute internally; if that theory falls apart in court, prosecutorial discretion can reverse just as fast as it appeared. Civil penalties under the Clean Air Act haven’t gone anywhere, and a shop or parts seller can still get hit with fines even with zero criminal risk attached. States aren’t necessarily bound by DOJ’s memo either. California’s air regulators have their own enforcement authority, and the federal government has been fighting California in court this past year over exactly how much of that authority survives federal preemption.
There’s also a quieter cost that outlasts any prosecution decision. A deleted emissions system is exactly the kind of aftermarket modification an insurer looks for after a claim, and finding one can be grounds to deny coverage on the truck itself or on damage a failed, untreated exhaust component contributes to down the road, a wrinkle worth understanding alongside the basics of how coverage and claims actually work. A manufacturer’s powertrain warranty typically excludes damage traceable to tampering with emissions hardware too, which means owners betting on lighter federal enforcement are still gambling with their own wallet, not the government’s.
It’s part of a broader pattern this year of regulators loosening the software leash on equipment manufacturers in some places while tightening it in others. The same year federal regulators forced John Deere to open up its repair software and diagnostic tools to independent shops, EPA is giving diesel engine manufacturers more room to decide how their own emissions software behaves out in the field. Anyone shopping a new heavy-duty truck once EPA’s rule is finalized should also read past the marketing about fewer roadside derates, since a shortened emissions warranty in the same proposal could shift real repair costs onto owners even as the derate headache disappears.
Congress never rewrote the Clean Air Act’s tampering provision. What changed in 2026 was who’s willing to enforce it, who gets a second chance after getting caught, and how much room manufacturers get to build into next year’s trucks. That’s a lot of policy resting on a memo, a pardon pen, and a proposed rule that hasn’t been finalized, which is worth remembering the next time someone claims deleting a diesel just got legal. It didn’t. The government just got a lot pickier about which cases it’s willing to bring.
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