US DOJ will no longer pursue criminal charges for motor vehicle emission tampering
23 January 2026
The US Department of Justice (DOJ) Environment and Natural Resources Division announced in a post on X that the DOJ will no longer pursue criminal charges under the Clean Air Act (CAA) related to tampering with onboard diagnostic devices in motor vehicles.
The DOJ said it is exercising its “enforcement discretion”. The agency has not provided reasons for the decision.
Emission tampering involves changes in hardware or software in in-use vehicles that impair the vehicle’s emission control system. Common examples include the installation of electronic “tuners” that reprogram the vehicle’s original software or “DPF delete” kits that allow the removal of particulate filters from diesel vehicles.
The DOJ will still “pursue civil enforcement for these violations when appropriate,” the agency said in their X post.
In 2020, the Environmental Protection Agency started the National Compliance Initiative (NCI) that pursued, in cooperation with the DOJ, emission violation enforcement in existing, in-use vehicles. Under the NCI program, the agency fined a number of suppliers and installers of tampering devices and software—referred to as illegal emission defeat devices. While most of the enforcement involved out of court settlements, some cases involved criminal penalties.
According to the EPA, under the NCI initiative, the agency finalized 172 civil enforcement cases from FY 2020 through FY 2023 resulting in civil penalties totaling $55.5 million. During the same period, the EPA completed 17 criminal cases resulting in penalties totaling $5.6 million, $1.2 million in restitution, $438,000 in environmental projects, and 54 months of incarceration.
However, the EPA web page does not provide details on enforcement activities during 2024 and 2025. In November 2025, a Wyoming diesel tuner who was imprisoned after being convicted on hundreds of counts of violating EPA emission regulations received an unconditional pardon from President Trump.
Source: US DOJ Environment and Natural Resources Division