The U.S. Department of Justice has made a significant change in how it enforces emissions laws related to diesel engines. Federal prosecutors have been instructed to stop pursuing criminal cases tied specifically to software-based diesel emissions “defeat devices.” While this move reduces criminal risk, it does not make diesel deletes legal, nor does it remove the financial and regulatory exposure facing trucking fleets and repair shops.
On January 21, the DOJ’s Environment and Natural Resources Division announced it would no longer pursue criminal charges under the Clean Air Act for cases involving tampering with onboard diagnostic (OBD) software. A memo from Deputy Attorney General Todd Blanche directed prosecutors to drop pending criminal cases and halt new ones related to emissions software manipulation.
What This Change Really Means
This decision marks a shift away from nearly a decade of aggressive criminal enforcement. However, it is important to understand what has — and has not — changed.
What has changed:
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Federal criminal prosecution for software-based emissions tampering is being deprioritized
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Shop owners and technicians face far less risk of indictment or prison time
What has not changed:
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Diesel emissions deletes are still illegal under federal law
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The EPA can still pursue civil enforcement
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State regulators, especially in CARB-aligned states, remain aggressive
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Civil penalties can still reach tens of thousands of dollars per vehicle
In short, the DOJ is stepping back from criminal cases, not giving the green light to emissions tampering.
Diesel Deletes in Heavy-Duty Trucking
Most public data on diesel deletes focuses on pickup trucks, but experts agree the practice likely exists across heavy-duty fleets as well. The reasons are familiar to many operators:
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High repair costs for emissions systems
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Downtime related to DPF and SCR failures
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Availability of aftermarket devices and online guides
However, even without criminal prosecution, fleets face serious consequences for tampering, including:
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Difficulty selling or trading in modified trucks
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Potential insurance coverage issues
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Voided OEM warranties
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Increased scrutiny during inspections or audits
Why the DOJ Shifted Its Approach
The policy change follows President Trump’s pardon of Troy Lake, a diesel shop owner who had pleaded guilty to disabling emissions monitoring systems on hundreds of heavy-duty trucks. That case highlighted how criminal enforcement had expanded beyond manufacturers to small businesses and technicians.
According to reports, DOJ leadership is now questioning whether emissions software qualifies as a component “required to be maintained” under the Clean Air Act for criminal liability. While this interpretation remains controversial, it has reshaped enforcement priorities.
Republican lawmakers, particularly from rural states, have long argued that criminal prosecutions unfairly targeted small repair shops rather than major polluters. The DOJ’s new stance reflects those concerns.
What Fleets and Shops Should Do Now
For trucking fleets and repair facilities, the reduced criminal risk may feel like relief, but it should not change compliance strategies.
Key takeaways for operators:
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Emissions deletes still carry heavy civil penalties
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EPA investigations are unchanged
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State enforcement remains a major risk
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Insurance and resale impacts can be severe
The shift primarily affects criminal exposure, not day-to-day compliance requirements. Fleets operating deleted trucks may still face costly fines, operational disruptions, and long-term asset value loss.
While fear of criminal prosecution has eased, the legal, financial, and regulatory risks tied to diesel emissions deletes remain firmly in place for the trucking industry.
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