The Justice Department on Wednesday, January 21, 2026, ordered federal prosecutors to stop pursuing criminal charges and drop all pending cases targeting the sale of illegal "defeat devices" that are used to tamper with air pollution control systems in diesel-powered vehicles. This is the first time that the Justice Department has formally taken steps to scale back environmental criminal enforcement since Trump took office in January 2025. Previous rollback of environmental rules targeting greenhouse gas emissions focused on civil enforcement rather than criminal enforcement.
What this means for Utah:
Mobile sources are a major pollution contributor, making up almost half of our total pollution.
EPA and state air quality planners consistently identify mobile sources (vehicles, trucks, buses, off-road equipment) as among the largest contributors to nitrogen oxides (NOx), particulate matter, and ozone precursors in many states, including Utah. (EPA planning data and state implementation plans reflect these categories as dominant pollutant sources, particularly in high-pollution areas like Salt Lake and Cache valleys.)
Because defeat devices and tampering disable primary emissions controls, they directly increase real-world emissions of NOx, particulate matter, and other harmful pollutants.
Federal deterrence is now weakened
Before this policy change:
Manufacturers and installers of defeat devices faced possible criminal prosecution, which acted as a strong deterrent.
Now:
Without criminal risk, some operators might be less constrained from selling, installing, or using emissions-disabling devices.Civil enforcement alone historically results in lower penalties and longer resolution timelines than criminal cases.
States and local enforcement become more important
As federal criminal enforcement weakens:
State environmental and vehicle emission laws, as well as State criminal statutes against tamperingmay take on greater importance. If a state has robust anti-tampering or anti-defeat device laws, those laws could still be enforced by state prosecutors. In places like Utah, which have serious air quality challenges and heavy mobile source pollution, the loss of federal criminal enforcement removes one enforcement “backstop” that helped ensure vehicles remained compliant with emissions controls, potentially making it harder to curb tampering-related pollution.
This new DOJ order could impact more than a dozen pending criminal cases across the country targeting companies and individuals who sold after-market emissions defeat devices, as well as more than 20 ongoing investigations.
